scholarly journals Critical Role for MyD88-Mediated Neutrophil Recruitment during Clostridium difficile Colitis

2012 ◽  
Vol 80 (9) ◽  
pp. 2989-2996 ◽  
Author(s):  
Irene Jarchum ◽  
Mingyu Liu ◽  
Chao Shi ◽  
Michele Equinda ◽  
Eric G. Pamer
Keyword(s):  
Clostridium Difficile ◽  
Inflammatory Responses ◽  
Adaptor Protein ◽  
Neutrophil Recruitment ◽  
Innate Immune ◽  
Antibiotic Administration ◽  
Immune Signaling ◽  
Content Type ◽  
Innate Immune Signaling ◽  
Deficient Mice

ABSTRACTClostridium difficilecan infect the large intestine and cause colitis when the normal intestinal microbiota is altered by antibiotic administration. Little is known about the innate immune signaling pathways that marshal inflammatory responses toC. difficileinfection and whether protective and pathogenic inflammatory responses can be dissociated. Toll-like receptors predominantly signal via the MyD88 adaptor protein and are important mediators of innate immune signaling in the intestinal mucosa. Here, we demonstrate that MyD88-mediated signals trigger neutrophil and CCR2-dependent Ly6Chimonocyte recruitment to the colonic lamina propria (cLP) during infection, which prevent dissemination of bystander bacteria to deeper tissues. Mortality is markedly increased in MyD88-deficient mice followingC. difficileinfection, as are parameters of mucosal tissue damage and inflammation. Antibody-mediated depletion of neutrophils markedly increases mortality, while attenuated recruitment of Ly6Chimonocytes in CCR2-deficient mice does not alter the course ofC. difficileinfection. Expression of CXCL1, a neutrophil-recruiting chemokine, is impaired in the cLP of MyD88−/−mice. Our studies suggest that MyD88-mediated signals promote neutrophil recruitment by inducing expression of CXCL1, thereby providing critical early defense againstC. difficile-mediated colitis.

scholarly journals Hepacivirus NS3/4A Proteases Interfere with MAVS Signaling in both Their Cognate Animal Hosts and Humans: Implications for Zoonotic Transmission

2016 ◽  
Vol 90 (23) ◽  
pp. 10670-10681 ◽  
Author(s):  
Anggakusuma ◽  
Richard J. P. Brown ◽  
Dominic H. Banda ◽  
Daniel Todt ◽  
Gabrielle Vieyres ◽  
...  
Keyword(s):  
Mammalian Species ◽  
Companion Animals ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Zoonotic Transmission ◽  
Common Mechanism ◽  
Zoonotic Potential ◽  
Immune Signaling ◽  
Content Type ◽  
Innate Immune Signaling

ABSTRACTMultiple novel members of the genusHepacivirushave recently been discovered in diverse mammalian species. However, to date, their replication mechanisms and zoonotic potential have not been explored in detail. The NS3/4A serine protease of hepatitis C virus (HCV) is critical for cleavage of the viral polyprotein. It also cleaves the cellular innate immune adaptor MAVS, thus decreasing interferon (IFN) production and contributing to HCV persistence in the human host. To investigate the conservation of fundamental aspects of the hepaciviral life cycle, we explored if MAVS cleavage and suppression of innate immune signaling represent a common mechanism employed across different clades of the genusHepacivirusto enhance viral replication. To estimate the zoonotic potential of these nonhuman hepaciviruses, we assessed if their NS3/4A proteases were capable of cleaving human MAVS. NS3/4A proteases of viruses infecting colobus monkeys, rodents, horses, and cows cleaved the MAVS proteins of their cognate hosts and interfered with the ability of MAVS to induce the IFN-β promoter. All NS3/4A proteases from nonhuman viruses readily cleaved human MAVS. Thus, NS3/4A-dependent cleavage of MAVS is a conserved replication strategy across multiple clades within the genusHepacivirus. Human MAVS is susceptible to cleavage by these nonhuman viral proteases, indicating that it does not pose a barrier for zoonotic transmission of these viruses to humans.IMPORTANCEVirus infection is recognized by cellular sensor proteins triggering innate immune signaling and antiviral defenses. While viruses have evolved strategies to thwart these antiviral programs in their cognate host species, these evasion mechanisms are often ineffective in a novel host, thus limiting viral transmission across species. HCV, the best-characterized member of the genusHepaciviruswithin the familyFlaviviridae, uses its NS3/4A protease to disrupt innate immune signaling by cleaving the cellular adaptor protein MAVS. Recently, a large number of HCV-related viruses have been discovered in various animal species, including wild, livestock, and companion animals. We show that the NS3/4A proteases of these hepaciviruses from different animals and representing various clades of the genus cleave their cognate host MAVS proteins in addition to human MAVS. Therefore, cleavage of MAVS is a common strategy of hepaciviruses, and human MAVS is likely unable to limit replication of these nonhuman viruses upon zoonotic exposure.

scholarly journals Interleukin-37 regulates innate immune signaling in human and mouse colonic organoids

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joannie M. Allaire ◽  
Anita Poon ◽  
Shauna M. Crowley ◽  
Xiao Han ◽  
Zohreh Sharafian ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Individual Variability ◽  
Innate Immune ◽  
Negative Regulator ◽  
Intestinal Epithelial ◽  
Immune Signaling ◽  
Strong Expression ◽  
Innate Immune Signaling ◽  
Close Proximity ◽  
Species Specific

AbstractIntestinal epithelial cells (IEC) reside in close proximity to the gut microbiota and are hypo-responsive to bacterial products, likely to prevent maladaptive inflammatory responses. This is in part due to their strong expression of Single Ig IL-1 related receptor (SIGIRR), a negative regulator of interleukin (IL)-1 and toll-like receptor signaling. IL-37 is an anti-inflammatory cytokine that inhibits innate signaling in diverse cells by signaling through SIGIRR. Despite the strong expression of SIGIRR by IEC, few studies have examined whether IL-37 can suppress their innate immune signaling. We characterized innate immune responses of human and murine colonoids to bacteria (FliC, LPS) and host (IL-1β) products and the role of IL-37/SIGIRR in regulating these responses. We demonstrated that human colonoids responded only to FliC, but not to LPS or IL-1β. While colonoids derived from different donors displayed significant inter-individual variability in the magnitude of their innate responses to FliC stimulation, all colonoids released a variety of chemokines. Interestingly, IL-37 attenuated these responses through inhibition of p38 and NFκB signaling pathways. We determined that this suppression by IL-37 was SIGIRR dependent, in murine organoids. Along with species-specific differences in IEC innate responses, we show that IL-37 can promote IEC hypo-responsiveness by suppressing inflammatory signaling.

scholarly journals Interleukin-37 Regulates Innate Immune Signaling in Human and Mouse Colonic Organoids

2020 ◽  
Author(s):  
Joannie Allaire ◽  
Anita Poon ◽  
Shauna Crowley ◽  
Xiao Han ◽  
Navjit Moore ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Individual Variability ◽  
Innate Immune ◽  
Negative Regulator ◽  
Intestinal Epithelial ◽  
Immune Signaling ◽  
Strong Expression ◽  
Innate Immune Signaling ◽  
Close Proximity ◽  
Species Specific

Abstract Intestinal epithelial cells (IEC) reside in close proximity to the gut microbiota and are hypo-responsive to bacterial products, likely to prevent maladaptive inflammatory responses. This is in part due to their strong expression of Single Ig IL-1 related receptor (SIGIRR), a negative regulator of interleukin (IL)-1 and toll-like receptor signaling. IL-37, an anti-inflammatory cytokine that inhibits innate signaling in diverse cells by signaling through SIGIRR. Despite the strong expression of SIGIRR by IEC, few studies have examined whether IL-37 can suppress their innate immune signaling. We characterized innate immune responses of human and murine colonoids to bacteria (FliC, LPS) and host (IL-1β) products and the role of IL-37/SIGIRR in regulating these responses. We demonstrated that human colonoids responded only to FliC, but not to LPS or IL-1β. While colonoids derived from different donors displayed significant inter-individual variability in the magnitude of their innate responses to FliC stimulation, all colonoids released a variety of chemokines. Interestingly, IL-37 attenuated these responses through inhibition of p38 and NFκB signaling pathways. We determined that this suppression by IL-37 was SIGIRR dependent, in murine organoids. Along with species-specific differences in IEC innate responses, we show that IL-37 can promote IEC hypo-responsiveness by supressing inflammatory signaling.

scholarly journals Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

2019 ◽  
Vol 99 (1) ◽  
pp. 893-948 ◽  
Author(s):  
Meng Xu ◽  
Peter P. Liu ◽  
Hongliang Li
Keyword(s):  
Transcription Factors ◽  
Immune System ◽  
Innate Immune System ◽  
Inflammatory Responses ◽  
Innate Immune ◽  
Immune Signaling ◽  
Cardiometabolic Diseases ◽  
Innate Immune Signaling ◽  
Cardiometabolic Disorders ◽  
Signaling Components

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

scholarly journals Distinct RIG-I and MDA5 Signaling by RNA Viruses in Innate Immunity

2007 ◽  
Vol 82 (1) ◽  
pp. 335-345 ◽  
Author(s):  
Yueh-Ming Loo ◽  
Jamie Fornek ◽  
Nanette Crochet ◽  
Gagan Bajwa ◽  
Olivia Perwitasari ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virus Infection ◽  
Influenza A Virus ◽  
Influenza A ◽  
Rna Viruses ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Influenza B ◽  
Immune Signaling ◽  
Innate Immune Signaling

ABSTRACT Alpha/beta interferon immune defenses are essential for resistance to viruses and can be triggered through the actions of the cytoplasmic helicases retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5). Signaling by each is initiated by the recognition of viral products such as RNA and occurs through downstream interaction with the IPS-1 adaptor protein. We directly compared the innate immune signaling requirements of representative viruses of the Flaviviridae, Orthomyxoviridae, Paramyxoviridae, and Reoviridae for RIG-I, MDA5, and interferon promoter-stimulating factor 1 (IPS-1). In cultured fibroblasts, IPS-1 was essential for innate immune signaling of downstream interferon regulatory factor 3 activation and interferon-stimulated gene expression, but the requirements for RIG-I and MDA5 were variable. Each was individually dispensable for signaling triggered by reovirus and dengue virus, whereas RIG-I was essential for signaling by influenza A virus, influenza B virus, and human respiratory syncytial virus. Functional genomics analyses identified cellular genes triggered during influenza A virus infection whose expression was strictly dependent on RIG-I and which are involved in processes of innate or adaptive immunity, apoptosis, cytokine signaling, and inflammation associated with the host response to contemporary and pandemic strains of influenza virus. These results define IPS-1-dependent signaling as an essential feature of host immunity to RNA virus infection. Our observations further demonstrate differential and redundant roles for RIG-I and MDA5 in pathogen recognition and innate immune signaling that may reflect unique and shared biologic properties of RNA viruses whose differential triggering and control of gene expression may impact pathogenesis and infection.

miRNAs, Immune Signaling, and Myelodysplastic Syndromes Pathogenesis

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. SCI-23-SCI-23
Author(s):  
Aly Karsan
Keyword(s):  
Acute Myeloid Leukemia ◽  
Myelodysplastic Syndromes ◽  
Myeloid Leukemia ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Low Risk ◽  
Immune Signaling ◽  
Innate Immune Signaling ◽  
The Impact ◽  
Acute Myeloid

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal stem cell hematologic malignancies characterized by cytopenias as a result of ineffective hematopoiesis and a propensity to progress to acute myeloid leukemia. In low-risk MDS, a characteristic finding in the bone marrow is that of increased apoptosis. The most common structural genomic aberration observed in MDS is the interstitial deletion of the long arm of chromosome 5. MDS with isolated del(5q) is a subtype of MDS characterized by severe anemia and variable neutropenia, but normal or high platelet counts with dysplastic megakaryocytes. MicroRNAs (miRNAs) are short noncoding RNAs capable of exerting their effects by postranscriptionally regulating numerous mRNA targets. We have shown that deletion of chromosome 5q correlates with loss miR-145 and miR-146a that are abundant in hematopoietic stem/progenitor cells (HSPC). Genes involved in innate immune signaling are significantly overrepresented when predicted targets of these two miRNas are surveyed. Specifically, Toll-interleukin-1 receptor domain-containing adaptor protein (TIRAP) and tumor necrosis factor receptor-associated factor-6 (TRAF6) are targets of miR-145 and miR-16a, respectively. Knockdown of miR-145 and miR-146a together or enforced expression of TRAF6, to activate innate immune signaling in mouse HSPC, results in thrombocytosis, mild neutropenia and megakaryocytic dysplasia. A subset of mice transplanted with TRAF6-expressing marrow, in order to aberrantly activate innate immune signaling, progress either to marrow failure or acute myeloid leukemia. Loss of these miRNAs and consequent inappropriate immune signaling results in suppression of HSPC with a relatively greater effect on normal HSPC. Thus, inappropriate activation of innate immune signaling in HSPC phenocopies several general clinical features of low-risk MDS and of del(5q) MDS in particular. Recent work from our group defines additional cytokine pathways that are dysregulated by loss of miR-143 and miR-145. The impact of cytokine dysregulation on HSPC and the marrow microenvironment will be discussed. Disclosures Karsan: Celgene: Research Funding.

scholarly journals Spatiotemporal dynamics of innate immune signaling via RIG-I–like receptors

2020 ◽  
Vol 117 (27) ◽  
pp. 15778-15788 ◽  
Author(s):  
Katharina Esser-Nobis ◽  
Lauren D. Hatfield ◽  
Michael Gale
Keyword(s):  
Innate Immunity ◽  
Virus Infection ◽  
Rna Virus ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Negative Regulator ◽  
Resting Cells ◽  
Immune Signaling ◽  
Innate Immune Signaling ◽  
Irf3 Activation

RIG-I, MDA5, and LGP2 comprise the RIG-I–like receptors (RLRs). RIG-I and MDA5 are essential pathogen recognition receptors sensing viral infections while LGP2 has been described as both RLR cofactor and negative regulator. After sensing and binding to viral RNA, including double-stranded RNA (dsRNA), RIG-I and MDA5 undergo cytosol-to-membrane relocalization to bind and signal through the MAVS adaptor protein on intracellular membranes, thus directing downstream activation of IRF3 and innate immunity. Here, we report examination of the dynamic subcellular localization of all three RLRs within the intracellular response to dsRNA and RNA virus infection. Observations from high resolution biochemical fractionation and electron microscopy, coupled with analysis of protein interactions and IRF3 activation, show that, in resting cells, microsome but not mitochondrial fractions harbor the central components to initiate innate immune signaling. LGP2 interacts with MAVS in microsomes, blocking the RIG-I/MAVS interaction. Remarkably, in response to dsRNA treatment or RNA virus infection, LGP2 is rapidly released from MAVS and redistributed to mitochondria, temporally correlating with IRF3 activation. We reveal that IRF3 activation does not take place on mitochondria but instead occurs at endoplasmic reticulum (ER)-derived membranes. Our observations suggest ER-derived membranes as key RLR signaling platforms controlled through inhibitory actions of LGP2 binding to MAVS wherein LGP2 translocation to mitochondria releases MAVS inhibition to facilitate RLR-mediated signaling of innate immunity.

scholarly journals Targeting CARD9 with Small-Molecule Therapeutics Inhibits Innate Immune Signaling and Inflammatory Response to Pneumocystis carinii β-Glucans

2020 ◽  
Vol 64 (11) ◽  
Author(s):  
Theodore J. Kottom ◽  
Eva M. Carmona ◽  
Andrew H. Limper
Keyword(s):  
Cell Wall ◽  
Small Molecule ◽  
Pneumocystis Carinii ◽  
Innate Immune ◽  
Necrosis Factor Alpha ◽  
Immune Signaling ◽  
Content Type ◽  
Innate Immune Signaling ◽  
Molecule Inhibitor ◽  
Small Molecule Therapeutics

ABSTRACT Pneumocystis jirovecii, the opportunistic fungus that causes Pneumocystis pneumonia (PCP) in humans, is a significant contributor to morbidity and mortality in immunocompromised patients. Given the profound deleterious inflammatory effects of the major β-glucan cell wall carbohydrate constituents of Pneumocystis through Dectin-1 engagement and downstream caspase recruitment domain-containing protein 9 (CARD9) immune activation, we sought to determine whether the pharmacodynamic activity of the known CARD9 inhibitor BRD5529 might have a therapeutic effect on macrophage innate immune signaling and subsequent downstream anti-inflammatory activity. The small-molecule inhibitor BRD5529 was able to significantly reduce both phospho-p38 and phospho-pERK1 signaling and tumor necrosis factor alpha (TNF-α) release during stimulation of macrophages with Pneumocystis cell wall β-glucans.

scholarly journals Native and aspirin-triggered lipoxins control innate immunity by inducing proteasomal degradation of TRAF6

2008 ◽  
Vol 205 (5) ◽  
pp. 1077-1086 ◽  
Author(s):  
Fabiana S. Machado ◽  
Lísia Esper ◽  
Alexandra Dias ◽  
Rajat Madan ◽  
YuanYuan Gu ◽  
...  
Keyword(s):  
Intracellular Signaling ◽  
Molecular Mechanisms ◽  
Inflammatory Responses ◽  
Interleukin 1 ◽  
Proteasomal Degradation ◽  
Innate Immune ◽  
Cytokine Signaling ◽  
Immune Signaling ◽  
Innate Immune Signaling

Innate immune signaling is critical for the development of protective immunity. Such signaling is, perforce, tightly controlled. Lipoxins (LXs) are eicosanoid mediators that play key counterregulatory roles during infection. The molecular mechanisms underlying LX-mediated control of innate immune signaling are of interest. In this study, we show that LX and aspirin (ASA)-triggered LX (ATL) inhibit innate immune signaling by inducing suppressor of cytokine signaling (SOCS) 2–dependent ubiquitinylation and proteasome-mediated degradation of TNF receptor–associated factor (TRAF) 2 and TRAF6, which are adaptor molecules that couple TNF and interleukin-1 receptor/Toll-like receptor family members to intracellular signaling events. LX-mediated degradation of TRAF6 inhibits proinflammatory cytokine production by dendritic cells. This restraint of innate immune signaling can be ablated by inhibition of proteasome function. In vivo, this leads to dysregulated immune responses, accompanied by increased mortality during infection. Proteasomal degradation of TRAF6 is a central mechanism underlying LX-driven immune counterregulation, and a hitherto unappreciated mechanism of action of ASA. These findings suggest a new molecular target for drug development for diseases marked by dysregulated inflammatory responses.

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