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Boukeileh S, Darawshi O, Shmuel M, Mahameed M, Wilhelm T, Dipta P, Forno F, Praveen B, Huber M, Levi-Schaffer F, Tirosh B. Endoplasmic Reticulum Homeostasis Regulates TLR4 Expression and Signaling in Mast Cells. Int J Mol Sci 2022; 23:ijms231911826. [PMID: 36233127 PMCID: PMC9569687 DOI: 10.3390/ijms231911826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 09/08/2022] [Accepted: 09/13/2022] [Indexed: 11/16/2022] Open
Abstract
The endoplasmic reticulum (ER) is a dynamic organelle that responds to demand in secretory proteins by undergoing expansion. The mechanisms that control the homeostasis of ER size and function involve the activation of the unfolded protein response (UPR). The UPR plays a role in various effector functions of immune cells. Mast cells (MCs) are highly granular tissue-resident cells and key drivers of allergic inflammation. Their diverse secretory functions in response to activation through the high-affinity receptor for IgE (FcεRI) suggest a role for the UPR in their function. Using human cord blood-derived MCs, we found that FcεRI triggering elevated the expression level and induced activation of the UPR transducers IRE1α and PERK, accompanied by expansion of the ER. In mouse bone marrow-derived MCs and peritoneal MCs, the ER underwent a more moderate expansion, and the UPR was not induced following MC activation. The deletion of IRE1α in mouse MCs did not affect proliferation, survival, degranulation, or cytokine stimulation following FcεRI triggering, but it did diminish the surface expression of TLR4 and the consequent response to LPS. A similar phenotype was observed in human MCs using an IRE1α inhibitor. Our data indicate that the ER of MCs, primarily of humans, undergoes a rapid remodeling in response to activation that promotes responses to TLR4. We suggest that IRE1α inhibition can be a strategy for inhibiting the hyperactivation of MCs by LPS over the course of allergic responses.
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Affiliation(s)
- Shatha Boukeileh
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Odai Darawshi
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Miriam Shmuel
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Mohamed Mahameed
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Thomas Wilhelm
- Institute of Biochemistry and Molecular Immunology, Medical School, RWTH Aachen University, D-52074 Aachen, Germany
| | - Priya Dipta
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Francesca Forno
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Bellam Praveen
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Michael Huber
- Institute of Biochemistry and Molecular Immunology, Medical School, RWTH Aachen University, D-52074 Aachen, Germany
| | - Francesca Levi-Schaffer
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
| | - Boaz Tirosh
- The School of Pharmacy, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 9112002, Israel
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
- Correspondence: or ; Tel.: +972-2-6758730; Fax: +972-2-6758741
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Zhang L, Stuber F, Lippuner C, Schiff M, Stamer UM. Phorbol-12-myristate-13-acetate induces nociceptin in human Mono Mac 6 cells via multiple transduction signalling pathways. Br J Anaesth 2016; 117:250-7. [PMID: 27307289 DOI: 10.1093/bja/aew063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/28/2016] [Indexed: 12/16/2023] Open
Abstract
BACKGROUND Nociceptin in the peripheral circulation has been proposed to have an immunoregulatory role with regards to inflammation and pain. However, the mechanisms involved in its regulation are still not clear. The aim of this study was to investigate signalling pathways contributing to the regulation of the expression of nociceptin under inflammatory conditions. METHODS Mono Mac 6 cells (MM6) were cultured with or without phorbol-12-myristate-13-acetate (PMA). Prepronociceptin (ppNOC) mRNA was detected by RT-qPCR and extracellular nociceptin by fluorescent-enzyme immunoassay. Intracellular nociceptin and phosphorylated kinases were measured using flow cytometry. To evaluate the contribution of various signalling pathways to the regulation of ppNOC mRNA and nociceptin protein, cells were pre-treated with specific kinase inhibitors before co-culturing with PMA. RESULTS ppNOC mRNA was expressed in untreated MM6 at low concentrations. Exposure of cells to PMA upregulated ppNOC after nine h compared with controls without PMA (median normalized ratio with IQR: 0.18 (0.15-0.26) vs. 0 (0-0.02), P<0.01). Inhibition of mitogen-activated protein kinases specific for signal transduction reversed the PMA effects (all P<0.001). Induction of nociceptin protein concentrations in PMA stimulated MM6 was prevented predominantly by identity of ERK inhibitor (P<0.05). CONCLUSIONS Upregulation of nociceptin expression by PMA in MM6 cells involves several pathways. Underlying mechanisms involved in nociceptin expression may lead to new insights in the treatment of pain and inflammatory diseases.
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Affiliation(s)
- L Zhang
- Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland
| | - F Stuber
- Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland
| | - C Lippuner
- Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland
| | - M Schiff
- Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland
| | - U M Stamer
- Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland
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Yiang GT, Chen JN, Wu TK, Wang HF, Hung YT, Chang WJ, Chen C, Wei CW, Yu YL. Ascorbic acid inhibits TPA-induced HL-60 cell differentiation by decreasing cellular H₂O₂ and ERK phosphorylation. Mol Med Rep 2015; 12:5501-7. [PMID: 26238149 DOI: 10.3892/mmr.2015.4091] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 05/27/2015] [Indexed: 11/06/2022] Open
Abstract
Retinoic acid (RA), vitamin D and 12-O‑tetradecanoyl phorbol-13-acetate (TPA) can induce HL-60 cells to differentiate into granulocytes, monocytes and macrophages, respectively. Similar to RA and vitamin D, ascorbic acid also belongs to the vitamin family. High‑dose ascorbic acid (>100 µM) induces HL‑60 cell apoptosis and induces a small fraction of HL‑60 cells to express the granulocyte marker, CD66b. In addition, ascorbic acid exerts an anti‑oxidative stress function. Oxidative stress is required for HL‑60 cell differentiation following treatment with TPA, however, the effect of ascorbic acid on HL‑60 cell differentiation in combination with TPA treatment remains to be fully elucidated. The aim of the present study was to investigate the cellular effects of ascorbic acid treatment on TPA-differentiated HL-60 cells. TPA-differentiated HL-60 cells were used for this investigation, this study and the levels of cellular hydrogen peroxide (H2O2), caspase activity and ERK phosphorylation were determined following combined treatment with TPA and ascorbic acid. The results demonstrated that low‑dose ascorbic acid (5 µM) reduced the cellular levels of H2O2 and inhibited the differentiation of HL‑60 cells into macrophages following treatment with TPA. In addition, the results of the present study further demonstrated that low‑dose ascorbic acid inactivates the ERK phosphorylation pathway, which inhibited HL‑60 cell differentiation following treatment with TPA.
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Affiliation(s)
- Giou-Teng Yiang
- Department of Emergency Medicine, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei 231, Taiwan, R.O.C
| | - Jen-Ni Chen
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan, R.O.C
| | - Tsai-Kun Wu
- The Ph.D. Program for Cancer Biology and Drug Discovery, China Medical University and Academia Sinica, Taichung 404, Taiwan, R.O.C
| | - Hsueh-Fang Wang
- Department of Nutrition, Master Program of Biomedical Nutrition, Hungkuang University, Taichung 433, Taiwan, R.O.C
| | - Yu-Ting Hung
- Department of Nutrition, Master Program of Biomedical Nutrition, Hungkuang University, Taichung 433, Taiwan, R.O.C
| | - Wei-Jung Chang
- Graduate Institute of Cancer Biology and Center for Molecular Medicine, China Medical University, Taichung 404, Taiwan, R.O.C
| | - Chinshuh Chen
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan, R.O.C
| | - Chyou-Wei Wei
- Department of Nutrition, Master Program of Biomedical Nutrition, Hungkuang University, Taichung 433, Taiwan, R.O.C
| | - Yung-Luen Yu
- The Ph.D. Program for Cancer Biology and Drug Discovery, China Medical University and Academia Sinica, Taichung 404, Taiwan, R.O.C
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Dulay AT, Buhimschi CS, Zhao G, Oliver EA, Abdel-Razeq SS, Shook LL, Bahtiyar MO, Buhimschi IA. Amniotic Fluid Soluble Myeloid Differentiation-2 (sMD-2) as Regulator of Intra-amniotic Inflammation in Infection-induced Preterm Birth. Am J Reprod Immunol 2015; 73:507-21. [PMID: 25605324 DOI: 10.1111/aji.12362] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 01/02/2015] [Indexed: 01/02/2023] Open
Abstract
PROBLEM TLR4 mediates host responses to pathogens through a mechanism that involves protein myeloid differentiation-2 (MD-2) and its soluble form sMD-2. The role of sMD2 in intra-amniotic inflammation-induced preterm birth has not been previously explored. METHOD OF STUDY Human amniotic fluid (AF) sMD-2 was studied by Western blotting in 152 AF samples of patients who had an amniocentesis to rule-out infection (yes infection, n = 50; no infection, n = 50) or women with normal pregnancy outcome (second trimester genetic karyotyping, n = 26; third trimester lung maturity testing, n = 26). Histological localization and mRNA expression of MD2 in fetal membranes were studied by immunohistochemistry and RT-PCR. The ability of fetal membrane to release sMD-2 and inflammatory cytokines was studied in vitro. RESULTS Human AF contains three sMD-2 proteoforms whose levels of expression were lower at term. Intra-amniotic infection upregulated sMD-2. MD-2 mRNA and immunohistochemistry findings concurred. In vitro, LPS and monensin increased, while cycloheximide decreased sMD-2 production. Recombinant sMD-2 modulated TNF-α and IL-6 levels in a dose- and time-dependent fashion. CONCLUSION sMD2 proteoforms are constitutively present in human AF. The intensity of the intra-amniotic inflammatory response to bacteria or perhaps to other TLR4 ligands may be facilitated through synthesis and release of sMD2 by the amniochorion.
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Affiliation(s)
- Antonette T Dulay
- Department of Obstetrics & Gynecology, The Ohio State University College of Medicine, Columbus, OH, USA.,Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA
| | - Catalin S Buhimschi
- Department of Obstetrics & Gynecology, The Ohio State University College of Medicine, Columbus, OH, USA.,Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Guomao Zhao
- Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA
| | - Emily A Oliver
- Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA
| | - Sonya S Abdel-Razeq
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, USA
| | - Lydia L Shook
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, USA
| | - Mert O Bahtiyar
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, USA
| | - Irina A Buhimschi
- Department of Obstetrics & Gynecology, The Ohio State University College of Medicine, Columbus, OH, USA.,Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
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Puiggròs F, Salvadó MJ, Bladé C, Arola L. Differential modulation of apoptotic processes by proanthocyanidins as a dietary strategy for delaying chronic pathologies. Crit Rev Food Sci Nutr 2014; 54:277-91. [PMID: 24188302 DOI: 10.1080/10408398.2011.565456] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Apoptosis is a biological process necessary for maintaining cellular homeostasis. Several diseases can result if it is deregulated. For example, inhibition of apoptotic signaling pathways is linked to the survival of pathological cells, which contributes to cancer, whereas excessive apoptosis is linked to neurodegenerative diseases, partially via oxidative stress. The activation or restoration of apoptosis via extrinsic or intrinsic pathways combined with cell signaling pathways triggered by reactive oxygen specises (ROS) formation is considered a key strategy by which bioactive foods can exert their health effects. Proanthocyanidins, a class of flavonoids naturally found in fruits, vegetables, and beverages, have attracted a great deal of attention not only because they are strong antioxidants but also because they appear to exert a different modulation of apoptosis, stimulating apoptosis in damaged cells, thus preventing cancer or reducing apoptosis in healthy cells, and as a result, preserving the integrity of normal cells and protecting against neurodegenerative diseases. Therefore, proanthocyanidins could provide a defense against apoptosis induced by oxidative stress or directly inhibit apoptosis, and they could also provide a promising treatment for a variety of diseases. Emerging data suggest that proanthocyanidins, especially those that humans can be persuaded to consume, may be used to prevent and manage cancer and mental disorders.
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Affiliation(s)
- Francesc Puiggròs
- a Nutrigenomics Group, Department of Biochemistry and Biotechnology , Universitat Rovira i Virgili , Tarragona , Spain
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Tanaka S, Masuda Y, Honma C, Hosaka K, Takahashi K, Kubohara Y. Manganese promotes phorbol ester-induced interleukin-2 production via AP-1 activation in Jurkat T-cells. Toxicol Lett 2012; 211:312-8. [DOI: 10.1016/j.toxlet.2012.04.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 04/19/2012] [Accepted: 04/20/2012] [Indexed: 10/28/2022]
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Schmeier S, MacPherson CR, Essack M, Kaur M, Schaefer U, Suzuki H, Hayashizaki Y, Bajic VB. Deciphering the transcriptional circuitry of microRNA genes expressed during human monocytic differentiation. BMC Genomics 2009; 10:595. [PMID: 20003307 PMCID: PMC2797535 DOI: 10.1186/1471-2164-10-595] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 12/10/2009] [Indexed: 12/19/2022] Open
Abstract
Background Macrophages are immune cells involved in various biological processes including host defence, homeostasis, differentiation, and organogenesis. Disruption of macrophage biology has been linked to increased pathogen infection, inflammation and malignant diseases. Differential gene expression observed in monocytic differentiation is primarily regulated by interacting transcription factors (TFs). Current research suggests that microRNAs (miRNAs) degrade and repress translation of mRNA, but also may target genes involved in differentiation. We focus on getting insights into the transcriptional circuitry regulating miRNA genes expressed during monocytic differentiation. Results We computationally analysed the transcriptional circuitry of miRNA genes during monocytic differentiation using in vitro time-course expression data for TFs and miRNAs. A set of TF→miRNA associations was derived from predicted TF binding sites in promoter regions of miRNA genes. Time-lagged expression correlation analysis was utilised to evaluate the TF→miRNA associations. Our analysis identified 12 TFs that potentially play a central role in regulating miRNAs throughout the differentiation process. Six of these 12 TFs (ATF2, E2F3, HOXA4, NFE2L1, SP3, and YY1) have not previously been described to be important for monocytic differentiation. The remaining six TFs are CEBPB, CREB1, ELK1, NFE2L2, RUNX1, and USF2. For several miRNAs (miR-21, miR-155, miR-424, and miR-17-92), we show how their inferred transcriptional regulation impacts monocytic differentiation. Conclusions The study demonstrates that miRNAs and their transcriptional regulatory control are integral molecular mechanisms during differentiation. Furthermore, it is the first study to decipher on a large-scale, how miRNAs are controlled by TFs during human monocytic differentiation. Subsequently, we have identified 12 candidate key controllers of miRNAs during this differentiation process.
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Affiliation(s)
- Sebastian Schmeier
- South African National Bioinformatics Institute, University of the Western Cape, Modderdam Road, Bellville, South Africa.
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Tissières P, Araud T, Ochoda A, Drifte G, Dunn-Siegrist I, Pugin J. Cooperation between PU.1 and CAAT/enhancer-binding protein beta is necessary to induce the expression of the MD-2 gene. J Biol Chem 2009; 284:26261-72. [PMID: 19632992 DOI: 10.1074/jbc.m109.042580] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Myeloid differentiation factor 2 (MD-2) binds Gram-negative bacterial lipopolysaccharide with high affinity and is essential for Toll-like receptor 4-dependent signal transduction. MD-2 has recently been recognized as a type II acute phase protein. Plasma concentrations of the soluble form of MD-2 increase markedly during the course of severe infections. Its production is regulated in hepatocytes and myeloid cells by interleukin-6 (IL-6) but not IL-1beta. In the present work we show that two transcription factors (TF), PU.1 and CAAT/enhancer-binding protein beta (C/EBPbeta), participate in the activation of the human MD-2 gene in hepatocytic cells after stimulation with IL-6. PU.1 TF and proximal PU.1 binding sites in the MD-2 promoter were shown to be critical for the basal activity of the promoter as well as for IL-6-induced soluble MD-2 production. Deletions of proximal portions of the MD-2 promoter containing PU.1 and/or NF-IL-6 consensus binding sites as well as site-directed mutagenesis of these binding sites abrogated IL-6-dependent MD-2 gene activation. We show that the cooperation between C/EBPbeta and PU.1 is critical for the transcriptional activation of the MD-2 gene by IL-6. PU.1 was essentially known as a TF involved in the differentiation of myeloid precursor cells and the expression of surface receptors of the innate immunity. Herein, we show that it also participates in the regulation of an acute phase protein, MD-2, in nonmyeloid cells cooperatively with C/EBPbeta, a classical IL-6-inducible TF.
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Affiliation(s)
- Pierre Tissières
- Intensive Care, University Hospitals of Geneva, Geneva 14, Switzerland
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Gao N, Budhraja A, Cheng S, Yao H, Zhang Z, Shi X. Induction of apoptosis in human leukemia cells by grape seed extract occurs via activation of c-Jun NH2-terminal kinase. Clin Cancer Res 2009; 15:140-9. [PMID: 19118041 DOI: 10.1158/1078-0432.ccr-08-1447] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
PURPOSE To characterize the functional role of c-Jun NH(2)-terminal kinase (JNK) and other apoptotic pathways in grape seed extract (GSE)-induced apoptosis in human leukemia cells by using pharmacologic and genetic approaches. EXPERIMENTAL DESIGN Jurkat cells were treated with various concentrations of GSE for 12 and 24 h or with 50 microg/mL GSE for various time intervals, after which apoptosis, caspase activation, and cell signaling pathways were evaluated. Parallel studies were done in U937 and HL-60 human leukemia cells. RESULTS Exposure of Jurkat cells to GSE resulted in dose- and time-dependent increase in apoptosis and caspase activation, events associated with the pronounced increase in Cip1/p21 protein level. Furthermore, treatment of Jurkat cells with GSE resulted in marked increase in levels of phospho-JNK. Conversely, interruption of the JNK pathway by pharmacologic inhibitor (e.g., SP600125) or genetic (e.g., small interfering RNA) approaches displayed significant protection against GSE-mediated lethality in Jurkat cells. CONCLUSIONS The result of the present study showed that GSE induces apoptosis in Jurkat cells through a process that involves sustained JNK activation and Cip1/p21 up-regulation, culminating in caspase activation.
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Affiliation(s)
- Ning Gao
- Department of Pharmacognosy, School of Pharmacy, 3rd Military Medical University, Chongqing, People's Republic of China
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Stimulation of Ebola virus production from persistent infection through activation of the Ras/MAPK pathway. Proc Natl Acad Sci U S A 2008; 105:17982-7. [PMID: 18981410 DOI: 10.1073/pnas.0809698105] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Human infections with Ebola virus (EBOV) result in a deadly viral disease known as Ebola hemorrhagic fever. Up to 90% of infected patients die, and there is no available treatment or vaccine. The sporadic human outbreaks are believed to result when EBOV "jumps" from an infected animal to a person and is subsequently transmitted between persons by direct contact with infected blood or body fluids. This study was undertaken to investigate the mechanism by which EBOV can persistently infect and then escape from model cell and animal reservoir systems. We report a model system in which infection of mouse and bat cell lines with EBOV leads to persistence, which can be broken with low levels of lipopolysaccharide or phorbol-12-myristate-13-acetate (PMA). This reactivation depends on the Ras/MAPK pathway through inhibition of RNA-dependent protein kinase and eukaryotic initiation factor 2alpha phosphorylation and occurs at the level of protein synthesis. EBOV also can be evoked from mice 7 days after infection by PMA treatment, indicating that a similar mechanism occurs in vivo. Our findings suggest that EBOV may persist in nature through subclinical infection of a reservoir species, such as bats, and that appropriate physiological stimulation may result in increased replication and transmission to new hosts. Identification of a presumptive mechanism responsible for EBOV emergence from its reservoir underscores the "hit-and-run" nature of the initiation of human and/or nonhuman primate EBOV outbreaks and may provide insight into possible countermeasures to interfere with transmission.
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