scholarly journals Connexin-Dependent Transfer of cGAMP to Phagocytes Modulates Antiviral Responses

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Geneviève Pépin ◽  
Dominic De Nardo ◽  
Christina L. Rootes ◽  
Tomalika R. Ullah ◽  
Sumaiah S. Al-Asmari ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Cyclic Gmp ◽  
Immune Cells ◽  
Feedback Loop ◽  
Direct Evidence ◽  
Critical Role ◽  
Positive Feedback Loop ◽  
Dna Viruses ◽  
Antiviral Responses ◽  
Infected Cells

ABSTRACT Activation of cyclic GMP-AMP (cGAMP) synthase (cGAS) plays a critical role in antiviral responses to many DNA viruses. Sensing of cytosolic DNA by cGAS results in synthesis of the endogenous second messenger cGAMP that activates stimulator of interferon genes (STING) in infected cells. Critically, cGAMP can also propagate antiviral responses to uninfected cells through intercellular transfer, although the modalities of this transfer between epithelial and immune cells remain poorly defined. We demonstrate here that cGAMP-producing epithelial cells can transactivate STING in cocultured macrophages through direct cGAMP transfer. cGAMP transfer was reliant upon connexin expression by epithelial cells and pharmacological inhibition of connexins blunted STING-dependent transactivation of the macrophage compartment. Macrophage transactivation by cGAMP contributed to a positive-feedback loop amplifying antiviral responses, significantly protecting uninfected epithelial cells against viral infection. Collectively, our findings constitute the first direct evidence of a connexin-dependent cGAMP transfer to macrophages by epithelial cells, to amplify antiviral responses. IMPORTANCE Recent studies suggest that extracellular cGAMP can be taken up by macrophages to engage STING through several mechanisms. Our work demonstrates that connexin-dependent communication between epithelial cells and macrophages plays a significant role in the amplification of antiviral responses mediated by cGAMP and suggests that pharmacological strategies aimed at modulating connexins may have therapeutic applications to control antiviral responses in humans.

scholarly journals FOXO3a regulates rhinovirus-induced innate immune responses in airway epithelial cells

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Joao Gimenes-Junior ◽  
Nicole Owuar ◽  
Hymavathi Reddy Vari ◽  
Wuyan Li ◽  
Nathaniel Xander ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Lung Inflammation ◽  
Inflammatory Cytokine ◽  
Airway Epithelial Cell ◽  
Critical Role ◽  
Airway Epithelial Cells ◽  
Type I ◽  
Airway Epithelial ◽  
Antiviral Responses

AbstractForkhead transcription factor class O (FOXO)3a, which plays a critical role in a wide variety of cellular processes, was also found to regulate cell-type-specific antiviral responses. Airway epithelial cells express FOXO3a and play an important role in clearing rhinovirus (RV) by mounting antiviral type I and type III interferon (IFN) responses. To elucidate the role of FOXO3a in regulating antiviral responses, we generated airway epithelial cell-specific Foxo3a knockout (Scga1b1-Foxo3a−/−) mice and a stable FOXO3a knockout human airway epithelial cell line. Compared to wild-type, Scga1b1-Foxo3a−/− mice show reduced IFN-α, IFN-β, IFN-λ2/3 in response to challenge with RV or double-stranded (ds)RNA mimic, Poly Inosinic-polycytidylic acid (Poly I:C) indicating defective dsRNA receptor signaling. RV-infected Scga1b1-Foxo3a−/− mice also show viral persistence, enhanced lung inflammation and elevated pro-inflammatory cytokine levels. FOXO3a K/O airway epithelial cells show attenuated IFN responses to RV infection and this was associated with conformational change in mitochondrial antiviral signaling protein (MAVS) but not with a reduction in the expression of dsRNA receptors under unstimulated conditions. Pretreatment with MitoTEMPO, a mitochondrial-specific antioxidant corrects MAVS conformation and restores antiviral IFN responses to subsequent RV infection in FOXO3a K/O cells. Inhibition of oxidative stress also reduces pro-inflammatory cytokine responses to RV in FOXO3a K/O cells. Together, our results indicate that FOXO3a plays a critical role in regulating antiviral responses as well as limiting pro-inflammatory cytokine expression. Based on these results, we conclude that FOXO3a contributes to optimal viral clearance and prevents excessive lung inflammation following RV infection.

scholarly journals N-chlorination mediates protective and immunomodulatory effects of oxidized human plasma proteins

2019 ◽  
Author(s):  
Agnes Ulfig ◽  
Anton V. Schulz ◽  
Alexandra Müller ◽  
Natalie Lupilov ◽  
Lars I. Leichert
Keyword(s):  
Immune Cells ◽  
Plasma Proteins ◽  
Feedback Loop ◽  
Hypochlorous Acid ◽  
Basic Amino Acid ◽  
Immunomodulatory Effects ◽  
Positive Feedback Loop ◽  
Amino Acid Side Chains ◽  
Blood Plasma Proteins ◽  
Reversible Nature

ABSTRACTHypochlorous acid (HOCl), a powerful antimicrobial oxidant, is produced by neutrophils to fight infections. Here we show thatN-chlorination, induced by HOCl concentrations encountered at sites of inflammation, converts blood plasma proteins into chaperone-like holdases that protect other proteins from aggregation. This chaperone-like conversion was reversible by antioxidants and was abrogated by prior methylation of basic amino acids. Furthermore, reversibleN-chlorination of basic amino acid side chains is the major factor that converts plasma proteins into efficient activators of immune cells. Finally, HOCl-modified serum albumin was found to act as a pro-survival molecule that protects neutrophils from cell death induced by highly immunogenic foreign antigens. We propose that activation and enhanced persistence of neutrophils mediated by HOCl-modified plasma proteins, resulting in the increased and prolonged generation of ROS, including HOCl, constitutes a potentially detrimental positive feedback loop that can only be attenuated through the reversible nature of the modification involved.

scholarly journals Interleukin 6 in inflammation, autoimmunity and cancer

2020 ◽  
Author(s):  
Toshio Hirano
Keyword(s):  
Chronic Inflammation ◽  
Immune Cells ◽  
Positive Feedback ◽  
Interleukin 6 ◽  
Feedback Loop ◽  
Inflammatory Responses ◽  
Virus Disease ◽  
Cytokine Storm ◽  
Necrosis Factor Alpha ◽  
Positive Feedback Loop

Abstract Interleukin 6 (IL-6) is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune cells and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is a NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6–STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6–STAT3 axis is a critical target for treating diseases.

scholarly journals A role for Jun-N-terminal kinase in anoikis; suppression by bcl-2 and crmA.

1996 ◽  
Vol 135 (5) ◽  
pp. 1377-1382 ◽  
Author(s):  
S M Frisch ◽  
K Vuori ◽  
D Kelaita ◽  
S Sicks
Keyword(s):  
Epithelial Cells ◽  
Cell Suspension ◽  
Information Flow ◽  
Feedback Loop ◽  
Early Response ◽  
Regulatory Proteins ◽  
Integrin Signaling ◽  
Positive Feedback Loop ◽  
Jnk Pathway ◽  
As Stress

The disruption of interactions between extracellular matrix and specific cognate integrins triggers apoptosis in epithelial cells, in a process termed "anoikis." To understand anoikis, the connections between epithelial cell integrin signaling and the apoptosis-regulatory proteins are being explored. We report herein that early after detachment from matrix, epithelial cells activate Jun-N-Terminal Kinases (JNKs; alternatively known as Stress-activated Protein Kinases), which are also activated by other apoptotic stimuli. The activity of this pathway was required for anoikis. Another early response to cell suspension was the activation of the ICE-related cysteine protease, ICE/LAP3; this activation and anoikis were suppressed by the ICE-protease inhibitor, crmA. The overexpression of bcl-2 suppressed ICE/LAP3 activation as well. Surprisingly, bcl-2 and crmA attenuated the activation of JNKs following cell suspension, suggesting that the JNK pathway is regulated directly or indirectly by proteolysis. In addition, the blockage of the JNK pathway attenuated the activation of ICE/LAP3, suggesting a positive feedback loop between the ICE and JNK systems. These results indicate the following sequence of information flow in anoikis: integrins-->bcl-2/bax-->(ICE-proteases<-->JNK)-->apopt osis. Cell-cell interactions, which were previously shown to sensitize cells to anoikis, caused bcl-2 mRNA to be downregulated, a permissive event for downstream apoptotic signaling.

scholarly journals The Positive Feedback Loop Between RLIP76 and HIF-1α Promotes Glycolysis and Tumorigenesis in Glioma Cells Under Hypoxic Conditions

2020 ◽  
Author(s):  
Qi Wang ◽  
Chi Zhang ◽  
Lei Zhang ◽  
Huairui Chen ◽  
Jun Qian ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Feedback Loop ◽  
Critical Role ◽  
Glioma Cells ◽  
U251 Cell ◽  
Positive Feedback Loop ◽  
Gene Therapy Approach ◽  
Hypoxic Conditions ◽  
Novel Target

Abstract BackgroundHypoxia is intimately associated with increased glycolysis in gliomas, and HIF-1α plays a critical role in this process. Here, we aim to show that RLIP76 is a novel target of HIF-1α and is involved in hypoxia-enhanced glycolysis in glioma cells. MethodsThe human glioma cell lines U87 and U251 were used to explore the interactions of RLIP76-HIF-1α and RLIP76-VHL using Western blot, a Biotin pull-down assay, Immunoprecipitation, and a Chromatin immunoprecipitation assay under hypoxia. U251 cells pretreated with hypoxia were used for tumor xenografts. ResultsRLIP76 is a novel target of HIF-1α and contributes to hypoxia-enhanced glycolysis in glioma cells. HIF-1α-induced RLIP76 can critically regulate the stability of HIF-1α by alleviating VHL-mediated HIF-1α ubiquitination under hypoxia. RLIP76 interacts with HIF-1α and VHL through an RLIP76 GAP-dependent mechanism. The GAP function of RLIP76 regulates its complex formation because of the dependence of RLIP76 GAP on interactions between RLIP76 and these proteins. RLIP76 knockdown results in decreased U251 cell growth after hypoxia pretreatment in vivo. ConclusionsThis study reveals a positive feedback loop between HIF-1α and RLIP76, suggesting that RLIP76 may undergo a complex series of GAP-dependent interactions with HIF-1α and VHL to protect HIF-1α from degradation while promoting glycolysis under hypoxic conditions. We indicate that RLIP76 is crucial for the regulation of hypoxia-enhanced glycolysis and may provide a new gene therapy approach for glioma patients.

scholarly journals Infection of lymphoid tissues in the macaque upper respiratory tract contributes to the emergence of transmissible measles virus

2013 ◽  
Vol 94 (9) ◽  
pp. 1933-1944 ◽  
Author(s):  
Martin Ludlow ◽  
Rory D. de Vries ◽  
Ken Lemon ◽  
Stephen McQuaid ◽  
Emma Millar ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Respiratory Tract ◽  
Immune Cells ◽  
Measles Virus ◽  
Upper Respiratory Tract ◽  
Free Virus ◽  
Cell Debris ◽  
Cell Layers ◽  
Infected Cells ◽  
Upper Respiratory

Measles virus (MV), a member of the family Paramyxoviridae, remains a major cause of morbidity and mortality in the developing world. MV is spread by aerosols but the mechanism(s) responsible for the high transmissibility of MV are largely unknown. We previously infected macaques with enhanced green fluorescent protein-expressing recombinant MV and euthanized them at a range of time points. In this study a comprehensive pathological analysis has been performed of tissues from the respiratory tract around the peak of virus replication. Isolation of virus from nose and throat swab samples showed that high levels of both cell-associated and cell-free virus were present in the upper respiratory tract. Analysis of tissue sections from lung and primary bronchus revealed localized infection of epithelial cells, concomitant infiltration of MV-infected immune cells into the epithelium and localized shedding of cells or cell debris into the lumen. While high numbers of MV-infected cells were present in the tongue, these were largely encapsulated by intact keratinocyte cell layers that likely limit virus transmission. In contrast, the integrity of tonsillar and adenoidal epithelia was disrupted with high numbers of MV-infected epithelial cells and infiltrating immune cells present throughout epithelial cell layers. Disruption was associated with large numbers of MV-infected cells or cell debris ‘spilling’ from epithelia into the respiratory tract. The coughing and sneezing response induced by disruption of the ciliated epithelium, leading to the expulsion of MV-infected cells, cell debris and cell-free virus, contributes to the highly infectious nature of MV.

scholarly journals The Major Component of IκBα Proteolysis Occurs Independently of the Proteasome Pathway in Respiratory Syncytial Virus-Infected Pulmonary Epithelial Cells

1998 ◽  
Vol 72 (6) ◽  
pp. 4849-4857 ◽  
Author(s):  
Mohammad Jamaluddin ◽  
Antonella Casola ◽  
Roberto P. Garofalo ◽  
Youqi Han ◽  
Todd Elliott ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Feedback Loop ◽  
A549 Cells ◽  
Fold Increase ◽  
26S Proteasome ◽  
Positive Feedback Loop ◽  
Tnf Α ◽  
Infected Cells ◽  
Proteasome Pathway ◽  
Syncytial Virus

ABSTRACT Previously we showed that infection of human type II airway epithelial (A549) cells with purified respiratory syncytial virus (pRSV) induced interleukin-8 transcription by a mechanism involving cytokine-inducible cytoplasmic-nuclear translocation of the RelA transcription factor. In unstimulated cells, RelA is tethered in the cytoplasm by association with the IκB inhibitor and can be released only following IκB degradation. In this study, we examined the spectrum of IκB isoform expression and kinetics of proteolysis of the isoforms in A549 cells following pRSV infection. In contrast to the rapid and robust activation of RelA DNA binding that peaked within 15 min of treatment produced by the prototypic activator tumor necrosis factor alpha (TNF-α), pRSV produced a weaker increase in RelA binding that began at 3 h and did not peak until 24 h after infection. A549 cells expressed the IκB inhibitory subunits IκBα, IκBβ, and p105; however, following either stimulus, only the IκBα and IκBβ steady-state levels declined in parallel with the increase in RelA DNA-binding activity. The >120-min half-life of IκBα in control cells was shortened to 5 min in TNF-α-stimulated cells and to 90 min in pRSV-infected cells. Although IκBα was resynthesized within 30 min following recombinant human TNFα treatment due to a robust 25-fold increase of IκBα mRNA expression (the RelA:IκBα positive feedback loop), following pRSV infection, there was no reaccumulation of IκBα protein, as infected cells produced only a 3-fold increase in IκBα mRNA at 24 h, indicating the RelA:IκBα positive feedback loop was insufficient to restore control IκBα levels. IκBα proteolysis induced by TNF-α occurred through the 26S proteasome, as both 26S proteasome activity and IκBα proteolysis were blocked by specific inhibitors lactacystin, MG-132, and ZLLF-CHO. Although total proteasome activity in 24-h pRSV-infected lysates increased twofold, its activity was >90% inhibited by the proteasome inhibitors; surprisingly, however, IκBα proteolysis was not. We conclude that RSV infection produces IκBα proteolysis through a mechanism primarily independent of the proteasome pathway.

scholarly journals A theoretical approach to coupling the epithelial-mesenchymal transition (EMT) to extracellular matrix (ECM) stiffness via LOXL2

2021 ◽  
Author(s):  
Youyuan Deng ◽  
Priyanka Chakraborty ◽  
Mohit Kumar Jolly ◽  
Herbert Levine
Keyword(s):  
Extracellular Matrix ◽  
Cancer Progression ◽  
Positive Feedback ◽  
Feedback Loop ◽  
Epithelial Mesenchymal Transition ◽  
Critical Role ◽  
Cross Linking ◽  
Positive Feedback Loop ◽  
Mesenchymal Transition ◽  
The Impact

AbstractThe epithelial-mesenchymal transition (EMT) plays a critical role in cancer progression, being responsible in many cases for the onset of the metastatic cascade and being integral in the ability of cells to resist drug treatment. Most studies of EMT focus on its induction via chemical signals such as TGF-β or Notch ligands, but it has become increasingly clear that biomechanical features of the microenvironment such as ECM (extracellular matrix) stiffness can be equally important. Here, we introduce a coupled feedback loop connecting stiffness to the EMT transcription factor ZEB1, which acts via increasing the secretion of LOXL2 that leads to increased cross-linking of collagen fibers in the ECM. This increased cross-linking can effectively increase ECM stiffness and increase ZEB1 levels, thus setting a positive feedback loop between ZEB1 and ECM stiffness. To investigate the impact of this non-cell-autonomous effect, we introduce a computational approach capable of connecting LOXL2 concentration to increased stiffness and thereby to higher ZEB1 levels. Our results indicate that this positive feedback loop, once activated, can effectively lock the cells in a mesenchymal state.

scholarly journals Glucocorticoids Promote the Onset of Acute Experimental Colitis and Cancer by Upregulating mTOR Signaling in Intestinal Epithelial Cells

Cancers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 945 ◽  
Author(s):  
Zhengguo Zhang ◽  
Lin Dong ◽  
Anna Jia ◽  
Xi Chen ◽  
Qiuli Yang ◽  
...  
Keyword(s):  
Ulcerative Colitis ◽  
Epithelial Cells ◽  
Immune Cells ◽  
Cytokine Production ◽  
Immune Cell ◽  
Intestinal Epithelial Cells ◽  
Critical Role ◽  
Mtor Signaling ◽  
Therapeutic Effects ◽  
Intestinal Epithelial

The therapeutic effects of glucocorticoids on colitis and colitis-associated cancer are unclear. In this study, we investigated the therapeutic roles of glucocorticoids in acute experimental ulcerative colitis and colitis-associated cancer in mice and their immunoregulatory mechanisms. Murine acute ulcerative colitis was induced by dextran sulfate sodium (DSS) and treated with dexamethasone (Dex) at different doses. Dex significantly exacerbated the onset and severity of DSS-induced colitis and potentiated mucosal inflammatory macrophage and neutrophil infiltration, as well as cytokine production. Furthermore, under inflammatory conditions, the expression of the glucocorticoid receptor (GR) did not change significantly, while mammalian target of rapamycin (mTOR) signaling was higher in colonic epithelial cells than in colonic immune cells. The deletion of mTOR in intestinal epithelial cells, but not that in myeloid immune cells, in mice significantly ameliorated the severe course of colitis caused by Dex, including weight loss, clinical score, colon length, pathological damage, inflammatory cell infiltration and pro-inflammatory cytokine production. These data suggest that mTOR signaling in intestinal epithelial cells, mainly mTORC1, plays a critical role in the Dex-induced exacerbation of acute colitis and colitis-associated cancer. Thus, these pieces of evidence indicate that glucocorticoid-induced mTOR signaling in epithelial cells is required in the early stages of acute ulcerative colitis by modulating the dynamics of innate immune cell recruitment and activation.

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