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Yang S, Zeng J, Yu J, Sun R, Tuo Y, Bai H. Insights into Chlamydia Development and Host Cells Response. Microorganisms 2024; 12:1302. [PMID: 39065071 PMCID: PMC11279054 DOI: 10.3390/microorganisms12071302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 06/15/2024] [Accepted: 06/23/2024] [Indexed: 07/28/2024] Open
Abstract
Chlamydia infections commonly afflict both humans and animals, resulting in significant morbidity and imposing a substantial socioeconomic burden worldwide. As an obligate intracellular pathogen, Chlamydia interacts with other cell organelles to obtain necessary nutrients and establishes an intracellular niche for the development of a biphasic intracellular cycle. Eventually, the host cells undergo lysis or extrusion, releasing infectious elementary bodies and facilitating the spread of infection. This review provides insights into Chlamydia development and host cell responses, summarizing the latest research on the biphasic developmental cycle, nutrient acquisition, intracellular metabolism, host cell fates following Chlamydia invasion, prevalent diseases associated with Chlamydia infection, treatment options, and vaccine prevention strategies. A comprehensive understanding of these mechanisms will contribute to a deeper comprehension of the intricate equilibrium between Chlamydia within host cells and the progression of human disease.
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Affiliation(s)
| | | | | | | | | | - Hong Bai
- Tianjin Key Laboratory of Cellular and Molecular Immunology (The Educational Ministry of China), Tianjin Institute of Immunology, Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China; (S.Y.); (J.Z.); (J.Y.); (R.S.); (Y.T.)
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2
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Cheong HC, Sulaiman S, Looi CY, Chang LY, Wong WF. Chlamydia Infection Remodels Host Cell Mitochondria to Alter Energy Metabolism and Subvert Apoptosis. Microorganisms 2023; 11:1382. [PMID: 37374883 DOI: 10.3390/microorganisms11061382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 06/29/2023] Open
Abstract
Chlamydia infection represents an important cause for concern for public health worldwide. Chlamydial infection of the genital tract in females is mostly asymptomatic at the early stage, often manifesting as mucopurulent cervicitis, urethritis, and salpingitis at the later stage; it has been associated with female infertility, spontaneous abortion, ectopic pregnancy, and cervical cancer. As an obligate intracellular bacterium, Chlamydia depends heavily on host cells for nutrient acquisition, energy production, and cell propagation. The current review discusses various strategies utilized by Chlamydia in manipulating the cell metabolism to benefit bacterial propagation and survival through close interaction with the host cell mitochondrial and apoptotic pathway molecules.
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Affiliation(s)
- Heng Choon Cheong
- Department of Medical Microbiology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Sofiah Sulaiman
- Department of Obstetrics and Gynaecology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Chung Yeng Looi
- School of Biosciences, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya 47500, Selangor, Malaysia
| | - Li-Yen Chang
- Department of Medical Microbiology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Won Fen Wong
- Department of Medical Microbiology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
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3
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Bacterial Infections and Atherosclerosis – A Mini Review. JOURNAL OF PURE AND APPLIED MICROBIOLOGY 2022. [DOI: 10.22207/jpam.16.3.08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Atherosclerosis is the most challenging subsets of coronary artery disease in humans, in which risk factors emerge from childhood, and its prevalence increases with age. Experimental research demonstrates that infections due to bacteria stimulate atherogenic events. Atherosclerosis has complex pathophysiology that is linked with several bacterial infections by damaging the inner arterial wall and heart muscles directly and indirectly by provoking a systemic pro-inflammation and acute-phase protein. Repeated bacterial infections trigger an inflammatory cascade that triggers immunological responses that negatively impact cardiovascular biomarkers includes triglycerides, high-density lipoprotein, C-reactive protein, heat shock proteins, cytokines, fibrinogen, and leukocyte count. Herein, we intended to share the role of bacterial infection in atherosclerosis and evaluate existing evidence of animal and human trials on the association between bacterial infections and atherosclerosis on update.
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4
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Sixt BS. Host cell death during infection with Chlamydia: a double-edged sword. FEMS Microbiol Rev 2021; 45:5902849. [PMID: 32897321 PMCID: PMC7794043 DOI: 10.1093/femsre/fuaa043] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 09/02/2020] [Indexed: 12/12/2022] Open
Abstract
The phylum Chlamydiae constitutes a group of obligate intracellular bacteria that infect a remarkably diverse range of host species. Some representatives are significant pathogens of clinical or veterinary importance. For instance, Chlamydia trachomatis is the leading infectious cause of blindness and the most common bacterial agent of sexually transmitted diseases. Chlamydiae are exceptionally dependent on their eukaryotic host cells as a consequence of their developmental biology. At the same time, host cell death is an integral part of the chlamydial infection cycle. It is therefore not surprising that the bacteria have evolved exquisite and versatile strategies to modulate host cell survival and death programs to their advantage. The recent introduction of tools for genetic modification of Chlamydia spp., in combination with our increasing awareness of the complexity of regulated cell death in eukaryotic cells, and in particular of its connections to cell-intrinsic immunity, has revived the interest in this virulence trait. However, recent advances also challenged long-standing assumptions and highlighted major knowledge gaps. This review summarizes current knowledge in the field and discusses possible directions for future research, which could lead us to a deeper understanding of Chlamydia's virulence strategies and may even inspire novel therapeutic approaches.
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Affiliation(s)
- Barbara S Sixt
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
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5
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Sajid M, Srivastava S, Joshi L, Bharadwaj M. Impact of smokeless tobacco-associated bacteriome in oral carcinogenesis. Anaerobe 2021; 70:102400. [PMID: 34090995 DOI: 10.1016/j.anaerobe.2021.102400] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/06/2021] [Accepted: 06/01/2021] [Indexed: 01/20/2023]
Abstract
Smokeless tobacco products possess a complex community of microorganisms. The microbial community ferment compounds present in the smokeless tobacco products and convert them into carcinogens like tobacco-associated nitrosamines. However, the potential of smokeless tobacco products associated bacteriome to manipulate systemic inflammation and other signaling pathways involved in the etiology of oral cancer will be a risk factor for oral cancer. Further, damage to oral epithelial cells causes a leaky oral layer that leads to increased infiltration of bacterial components like lipopolysaccharide, flagellin, and toxins, etc. The consumption of smokeless tobacco products can cause damage to the oral layer and dysbiosis of oral microbiota. Hence, the enrichment of harmful microbes due to dysbiosis in the oral cavity can produce high levels of bacterial metabolites and provoke inflammation as well as carcinogenesis. Understanding the complex and dynamic interrelation between the smokeless tobacco-linked bacteriome and host oral microbiome may help to unravel the mechanism of oral carcinogenesis stimulated by smokeless tobacco products. This review provides an insight into smokeless tobacco product-associated bacteriome and their potential in the progression of oral cancer. In the future, this will guide in the evolution of prevention and treatment strategies against smokeless tobacco products-induced oral cancer. Besides, it will assist the government organizations for better management and cessation policy building for the worldwide problem of smokeless tobacco addiction.
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Affiliation(s)
- Mohammad Sajid
- Molecular Genetics and Biochemistry, National Institute of Cancer Prevention and Research, Indian Council of Medical Research (ICMR), Sector-39, Noida, 201301, India
| | - Sonal Srivastava
- Molecular Genetics and Biochemistry, National Institute of Cancer Prevention and Research, Indian Council of Medical Research (ICMR), Sector-39, Noida, 201301, India
| | - Lata Joshi
- Molecular Genetics and Biochemistry, National Institute of Cancer Prevention and Research, Indian Council of Medical Research (ICMR), Sector-39, Noida, 201301, India
| | - Mausumi Bharadwaj
- Molecular Genetics and Biochemistry, National Institute of Cancer Prevention and Research, Indian Council of Medical Research (ICMR), Sector-39, Noida, 201301, India.
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6
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Zhong W, Darville T, Zheng X, Fine J, Li Y. Generalized multi-SNP mediation intersection-union test. Biometrics 2020; 78:364-375. [PMID: 33316078 DOI: 10.1111/biom.13418] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 11/23/2020] [Accepted: 12/04/2020] [Indexed: 12/15/2022]
Abstract
To elucidate the molecular mechanisms underlying genetic variants identified from genome-wide association studies (GWAS) for a variety of phenotypic traits encompassing binary, continuous, count, and survival outcomes, we propose a novel and flexible method to test for mediation that can simultaneously accommodate multiple genetic variants and different types of outcome variables. Specifically, we employ the intersection-union test approach combined with the likelihood ratio test to detect mediation effect of multiple genetic variants via some mediator (e.g., the expression of a neighboring gene) on outcome. We fit high-dimensional generalized linear mixed models under the mediation framework, separately under the null and alternative hypothesis. We leverage Laplace approximation to compute the marginal likelihood of outcome and use coordinate descent algorithm to estimate corresponding parameters. Our extensive simulations demonstrate the validity of our proposed methods and substantial, up to 97%, power gains over alternative methods. Applications to real data for the study of Chlamydia trachomatis infection further showcase advantages of our methods. We believe our proposed methods will be of value and general interest in this post-GWAS era to disentangle the potential causal mechanism from DNA to phenotype for new drug discovery and personalized medicine.
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Affiliation(s)
- Wujuan Zhong
- Department of Biostatistics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Toni Darville
- Department of Pediatrics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Xiaojing Zheng
- Department of Biostatistics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.,Department of Pediatrics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Jason Fine
- Department of Biostatistics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.,Department of Statistics and Operations Research, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Yun Li
- Department of Biostatistics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.,Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.,Department of Computer Science, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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7
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Chen Y, Sheppard D, Dong X, Hu X, Chen M, Chen R, Chakrabarti J, Zavros Y, Peek RM, Chen LF. H. pylori infection confers resistance to apoptosis via Brd4-dependent BIRC3 eRNA synthesis. Cell Death Dis 2020; 11:667. [PMID: 32820150 PMCID: PMC7441315 DOI: 10.1038/s41419-020-02894-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 07/28/2020] [Accepted: 07/29/2020] [Indexed: 02/07/2023]
Abstract
H. pylori infection is one of the leading causes of gastric cancer and the pathogenicity of H. pylori infection is associated with its ability to induce chronic inflammation and apoptosis resistance. While H. pylori infection-induced expression of pro-inflammatory cytokines for chronic inflammation is well studied, the molecular mechanism underlying the apoptosis resistance in infected cells is not well understood. In this study, we demonstrated that H. pylori infection-induced apoptosis resistance in gastric epithelial cells triggered by Raptinal, a drug that directly activates caspase-3. This resistance resulted from the induction of cIAP2 (encoded by BIRC3) since depletion of BIRC3 by siRNA or inhibition of cIAP2 via BV6 reversed H. pylori-suppressed caspase-3 activation. The induction of cIAP2 was regulated by H. pylori-induced BIRC3 eRNA synthesis. Depletion of BIRC3 eRNA decreased H. pylori-induced cIAP2 and reversed H. pylori-suppressed caspase-3 activation. Mechanistically, H. pylori stimulated the recruitment of bromodomain-containing factor Brd4 to the enhancer of BIRC3 and promoted BIRC3 eRNA and mRNA synthesis. Inhibition of Brd4 diminished the expression of BIRC3 eRNA and the anti-apoptotic response to H. pylori infection. Importantly, H. pylori isogenic cagA-deficient mutant failed to activate the synthesis of BIRC3 eRNA and the associated apoptosis resistance. Finally, in primary human gastric epithelial cells, H. pylori also induced resistance to Raptinal-triggered caspase-3 activation by activating the Brd4-dependent BIRC3 eRNA synthesis in a CagA-dependent manner. These results identify a novel function of Brd4 in H. pylori-mediated apoptosis resistance via activating BIRC3 eRNA synthesis, suggesting that Brd4 could be a potential therapeutic target for H. pylori-induced gastric cancer.
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Affiliation(s)
- Yanheng Chen
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, 61801, IL, USA
| | - Donald Sheppard
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, 61801, IL, USA
| | - Xingchen Dong
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, 61801, IL, USA
| | - Xiangming Hu
- Fujian Key Laboratory for Translational Research in Cancer and Neurodegenerative Diseases, Institute for Translational Medicine, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, 350122, China
| | - Meihua Chen
- The State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, 361101, China
| | - Ruichuan Chen
- The State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, 361101, China
| | - Jayati Chakrabarti
- Department of Pharmacology and Systems Physiology, University of Cincinnati, Cincinnati, 45267, OH, USA
- Department of Cellular and Molevular Medicine, College of Medicine, University of Arizona-Tucson, Tucson, 85724, AZ, USA
| | - Yana Zavros
- Department of Pharmacology and Systems Physiology, University of Cincinnati, Cincinnati, 45267, OH, USA
- Department of Cellular and Molevular Medicine, College of Medicine, University of Arizona-Tucson, Tucson, 85724, AZ, USA
| | - Richard M Peek
- Division of Gastroenterology, Department of Medicine and Cancer Biology, Vanderbilt University School of Medicine, Nashville, 37232, TN, USA
| | - Lin-Feng Chen
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, 61801, IL, USA.
- Carle R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, 61801, IL, USA.
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8
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Li Y, Wang X, Wang X, Wan L, Liu Y, Shi Y, Zhang L, Fang Z, Wei Z. PDCD4 suppresses proliferation, migration, and invasion of endometrial cells by inhibiting autophagy and NF-κB/MMP2/MMP9 signal pathway. Biol Reprod 2019; 99:360-372. [PMID: 29912279 DOI: 10.1093/biolre/ioy052] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Accepted: 06/14/2018] [Indexed: 11/12/2022] Open
Abstract
Endometriosis (EM) is a kind of estrogen-dependent disease in reproductive-age women. Ovarian EM is the most common type. Although EM is a benign disease, it shares many similar features with cancers. Programmed cell death 4 (PDCD4), a newly identified tumor suppressor, plays an important role in inhibiting tumorigenesis and tumor progression at the transcriptional and translational levels. To explore the roles of PDCD4 in EM, we detected the expression of PDCD4 in control endometrium and eutopic/ectopic endometrium of ovarian EM patients, and analyzed the effects of PDCD4 on the biological behaviors of endometrial cell lines and primary endometrial cells. The results demonstrated that PDCD4 was downregulated in eutopic and ectopic endometrium of EM patients compared with control endometrium. PDCD4 effectively inhibited the proliferation and colony-forming ability of endometrial cells maybe by inhibiting cell autophagy. In addition, PDCD4 also suppressed the migration and invasion ability of endometrial cells, the mechanism may be related to NF-κB/MMP2/MMP9 signal pathway. Taken together, these results suggest that PDCD4 could be involved in the pathogenesis of EM, and provide a novel approach to target the aberrant PDCD4 expression in EM.
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Affiliation(s)
- Yue Li
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China
| | - Xiaoyan Wang
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China
| | - Xishuang Wang
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China
| | - Lu Wan
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China
| | - Yanping Liu
- Department of Gynecology and Obstetrics, Jinan Central Hospital affiliated to Shandong University, Jinan, Shandong, P. R. China
| | - Yongyu Shi
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China
| | - Lining Zhang
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China
| | - Zhenghui Fang
- Department of Gynecology and Obstetrics, Jinan Central Hospital affiliated to Shandong University, Jinan, Shandong, P. R. China
| | - Zengtao Wei
- Department of Immunology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, P. R. China.,Department of Gynecology and Obstetrics, Jinan Central Hospital affiliated to Shandong University, Jinan, Shandong, P. R. China.,Department of Gynecology and Obstetrics, Clinical Medical School, Shandong University, Jinan, Shandong, P. R. China
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9
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Horn J, Stelzner K, Rudel T, Fraunholz M. Inside job: Staphylococcus aureus host-pathogen interactions. Int J Med Microbiol 2017; 308:607-624. [PMID: 29217333 DOI: 10.1016/j.ijmm.2017.11.009] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 11/17/2017] [Accepted: 11/21/2017] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is a notorious opportunistic pathogen causing a plethora of diseases. Recent research established that once phagocytosed by neutrophils and macrophages, a certain percentage of S. aureus is able to survive within these phagocytes which thereby even may contribute to dissemination of the pathogen. S. aureus further induces its uptake by otherwise non-phagocytic cells and the ensuing intracellular cytotoxicity is suggested to lead to tissue destruction, whereas bacterial persistence within cells is thought to lead to immune evasion and chronicity of infections. We here review recent work on the S. aureus host pathogen interactions with a focus on the intracellular survival of the pathogen.
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Affiliation(s)
- Jessica Horn
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Kathrin Stelzner
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Thomas Rudel
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Martin Fraunholz
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
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10
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Pothineni NVK, Subramany S, Kuriakose K, Shirazi LF, Romeo F, Shah PK, Mehta JL. Infections, atherosclerosis, and coronary heart disease. Eur Heart J 2017; 38:3195-3201. [DOI: 10.1093/eurheartj/ehx362] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 06/06/2017] [Indexed: 12/22/2022] Open
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11
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Robinson KS, Aw R. The Commonalities in Bacterial Effector Inhibition of Apoptosis. Trends Microbiol 2016; 24:665-680. [PMID: 27117049 DOI: 10.1016/j.tim.2016.04.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 03/13/2016] [Accepted: 04/01/2016] [Indexed: 02/09/2023]
Abstract
Antiapoptotic pathways of the host cell play integral roles in bacterial pathogenesis, with inhibition of those pathways resulting in halted disease pathology. Certain pathogens have developed elegant mechanisms to modulate the fate of the host cell, many of which target novel pathways that are poorly understood in the context of the cell biology. Bacterial pathogenesis research not only promotes the understanding of the role of antiapoptotic pathways in bacterial infection, but has a broader context in understanding the epitome of human disease, that is, developing the understanding of tumorigenic or inflammatory pathways. Here we review host antiapoptotic signalling pathways manipulated by translocated bacterial effectors that propagate the disease state, drawing common parallels and showing the novel differences.
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Affiliation(s)
- Keith S Robinson
- Department of Life Science, Imperial College London, London, UK.
| | - Rochelle Aw
- Department of Life Science, Imperial College London, London, UK
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12
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Fischer A, Rudel T. Subversion of Cell-Autonomous Host Defense by Chlamydia Infection. Curr Top Microbiol Immunol 2016; 412:81-106. [PMID: 27169422 DOI: 10.1007/82_2016_13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Obligate intracellular bacteria entirely depend on the metabolites of their host cell for survival and generation of progeny. Due to their lifestyle inside a eukaryotic cell and the lack of any extracellular niche, they have to perfectly adapt to compartmentalized intracellular environment of the host cell and counteract the numerous defense strategies intrinsically present in all eukaryotic cells. This so-called cell-autonomous defense is present in all cell types encountering Chlamydia infection and is in addition closely linked to the cellular innate immune defense of the mammalian host. Cell type and chlamydial species-restricted mechanisms point a long-term evolutionary adaptation that builds the basis of the currently observed host and cell-type tropism among different Chlamydia species. This review will summarize the current knowledge on the strategies pathogenic Chlamydia species have developed to subvert and overcome the multiple mechanisms by which eukaryotic cells defend themselves against intracellular pathogens.
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Affiliation(s)
- Annette Fischer
- Department of Microbiology and Biocenter, University of Würzburg, Am Hubland, 97074, Wuerzburg, Germany
| | - Thomas Rudel
- Department of Microbiology and Biocenter, University of Würzburg, Am Hubland, 97074, Wuerzburg, Germany.
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13
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Sarkar A, Möller S, Bhattacharyya A, Behnen M, Rupp J, van Zandbergen G, Solbach W, Laskay T. Mechanisms of apoptosis inhibition in Chlamydia pneumoniae-infected neutrophils. Int J Med Microbiol 2015; 305:493-500. [PMID: 26005182 DOI: 10.1016/j.ijmm.2015.04.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 02/27/2015] [Accepted: 04/28/2015] [Indexed: 11/20/2022] Open
Abstract
The obligatory intracellular bacterium Chlamydia pneumoniae (C. pneumoniae) can survive and multiply in neutrophil granulocytes. Since neutrophils are short living cells, inhibition of neutrophil apoptosis appears to play a major role in the productive infection of neutrophils by C. pneumoniae. In the present study, we have investigated which survival pathways and which events of the apoptotic process are modulated in C. pneumoniae-infected neutrophils. All infection experiments were carried out using primary human neutrophils in vitro. We show that infection with C. pneumoniae activates PI3K/Akt as well as the ERK1/2 and p38 MAP kinases and present evidence that activation of the PI3K/Akt and ERK1/2 pathways are essential to initiate the apoptosis delay in C. pneumoniae-infected neutrophils. Both the PI3K/Akt and ERK1/2 pathways are involved in the maintained expression of the anti-apoptotic protein Mcl-1. In addition, we also showed that the PI3K/Akt pathway leads to the activation of NF-κB-dependent release of IL-8 by infected neutrophils. Infection with C. pneumoniae activates the PI3K/Akt and ERK1/2 MAPK survival pathways in neutrophils, induces the NF-κB dependent release of IL-8 and leads to the maintenance of Mcl-1 expression in neutrophils.
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Affiliation(s)
- Arup Sarkar
- Institute for Medical Microbiology and Hygiene, University of Lübeck, German Center for Infection Research (DZIF), Ratzeburger Allee 160, D-23538 Lübeck, Germany.
| | - Sonja Möller
- Institute for Medical Microbiology and Hygiene, University of Lübeck, German Center for Infection Research (DZIF), Ratzeburger Allee 160, D-23538 Lübeck, Germany
| | - Asima Bhattacharyya
- National Institute of Science Education and Research, School of Biological Sciences, Bhubaneswar 751005, Odisha, India
| | - Martina Behnen
- Institute for Medical Microbiology and Hygiene, University of Lübeck, German Center for Infection Research (DZIF), Ratzeburger Allee 160, D-23538 Lübeck, Germany
| | - Jan Rupp
- Institute for Medical Microbiology and Hygiene, University of Lübeck, German Center for Infection Research (DZIF), Ratzeburger Allee 160, D-23538 Lübeck, Germany
| | | | - Werner Solbach
- Institute for Medical Microbiology and Hygiene, University of Lübeck, German Center for Infection Research (DZIF), Ratzeburger Allee 160, D-23538 Lübeck, Germany
| | - Tamás Laskay
- Institute for Medical Microbiology and Hygiene, University of Lübeck, German Center for Infection Research (DZIF), Ratzeburger Allee 160, D-23538 Lübeck, Germany.
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14
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Dlugosz A, Muschiol S, Zakikhany K, Assadi G, D'Amato M, Lindberg G. Human enteroendocrine cell responses to infection with Chlamydia trachomatis: a microarray study. Gut Pathog 2014; 6:24. [PMID: 24959205 PMCID: PMC4067063 DOI: 10.1186/1757-4749-6-24] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Accepted: 06/12/2014] [Indexed: 12/20/2022] Open
Abstract
Background Enteroendocrine cells (EEC) are highly specialized cells producing signalling molecules vital to the normal functions of the gut. Recently, we showed altered protein distribution in Chlamydia infected EEC in vitro. The aim of this study was to perform a microarray analysis of the response pattern of EEC from both large and small bowel to infection in vitro, using Chlamydia trachomatis infection as a model. Methods Two human EEC lines: LCC-18, derived from a neuroendocrine colonic tumour, and CNDT-2, derived from a small intestinal carcinoid, were infected using cultured C. trachomatis serovar LGV II strain 434 (ATCC VR-902B). Penicillin G was used to induce persistent infection. We used microarray analysis (Affymetrix GeneChip®) for studying changes in gene expression at different stages of infection. Results Twenty-four hours after active and persistent infection, 66 and 411 genes in LCC-18 and 68 and 170 genes in CNDT-2 cells, respectively showed mean expression ratios >2-fold compared to non-infected cells. These genes encoded factors regulating apoptosis, cell differentiation, transcription regulation, cytokine activity, amine biosynthesis and vesicular transport. We found significant differences in gene transcription levels between persistently infected and non-infected cells in 10 genes coding for different solute carrier transporters (SLC) and in 5 genes related to endocrine function (GABARAPL1, GRIP1, DRD2, SYT5 and SYT7). Conclusions Infected EEC cells exhibit cell-type specific patterns related to vesicular transport, secretion and neurotransmitters. EEC play a pivotal role in regulation of gut motility and an impairment of enteroendocrine function can contribute to motility disorders.
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Affiliation(s)
- Aldona Dlugosz
- Karolinska Institutet, Department of Medicine, Division of Gastroenterology and Hepatology, Karolinska University Hospital, Gastrocentrum Huddinge K63, Stockholm, Sweden
| | - Sandra Muschiol
- Karolinska Institutet, Department of Microbiology, Tumor and Cell Biology (MTC), Stockholm, Sweden
| | | | - Ghazaleh Assadi
- Karolinska Institutet, Department of Biosciences and Nutrition, Stockholm, Sweden
| | - Mauro D'Amato
- Karolinska Institutet, Department of Biosciences and Nutrition, Stockholm, Sweden
| | - Greger Lindberg
- Karolinska Institutet, Department of Medicine, Division of Gastroenterology and Hepatology, Karolinska University Hospital, Gastrocentrum Huddinge K63, Stockholm, Sweden
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15
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Parthasarathy G, Philipp MT. Review: apoptotic mechanisms in bacterial infections of the central nervous system. Front Immunol 2012; 3:306. [PMID: 23060884 PMCID: PMC3463897 DOI: 10.3389/fimmu.2012.00306] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 09/15/2012] [Indexed: 01/18/2023] Open
Abstract
In this article we review the apoptotic mechanisms most frequently encountered in bacterial infections of the central nervous system (CNS). We focus specifically on apoptosis of neural cells (neurons and glia), and provide first an overview of the phenomenon of apoptosis itself and its extrinsic and intrinsic pathways. We then describe apoptosis in the context of infectious diseases and inflammation caused by bacteria, and review its role in the pathogenesis of the most relevant bacterial infections of the CNS.
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Affiliation(s)
- Geetha Parthasarathy
- Division of Bacteriology and Parasitology, Tulane National Primate Research Center, Tulane University Covington, LA, USA
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16
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De Chiara G, Marcocci ME, Sgarbanti R, Civitelli L, Ripoli C, Piacentini R, Garaci E, Grassi C, Palamara AT. Infectious agents and neurodegeneration. Mol Neurobiol 2012; 46:614-38. [PMID: 22899188 PMCID: PMC3496540 DOI: 10.1007/s12035-012-8320-7] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 07/31/2012] [Indexed: 12/19/2022]
Abstract
A growing body of epidemiologic and experimental data point to chronic bacterial and viral infections as possible risk factors for neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Infections of the central nervous system, especially those characterized by a chronic progressive course, may produce multiple damage in infected and neighbouring cells. The activation of inflammatory processes and host immune responses cause chronic damage resulting in alterations of neuronal function and viability, but different pathogens can also directly trigger neurotoxic pathways. Indeed, viral and microbial agents have been reported to produce molecular hallmarks of neurodegeneration, such as the production and deposit of misfolded protein aggregates, oxidative stress, deficient autophagic processes, synaptopathies and neuronal death. These effects may act in synergy with other recognized risk factors, such as aging, concomitant metabolic diseases and the host’s specific genetic signature. This review will focus on the contribution given to neurodegeneration by herpes simplex type-1, human immunodeficiency and influenza viruses, and by Chlamydia pneumoniae.
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Affiliation(s)
- Giovanna De Chiara
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Rome, Italy.
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17
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Shao R, Wang X, Wang W, Stener-Victorin E, Mallard C, Brännström M, Billig H. From mice to women and back again: causalities and clues for Chlamydia-induced tubal ectopic pregnancy. Fertil Steril 2012; 98:1175-85. [PMID: 22884019 DOI: 10.1016/j.fertnstert.2012.07.1113] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 07/12/2012] [Accepted: 07/12/2012] [Indexed: 01/12/2023]
Abstract
OBJECTIVE To provide an overview of knockout mouse models that have pathological tubal phenotypes after Chlamydia muridarum infection, discuss factors and pathological processes that contribute to inflammation, summarize data on tubal transport and progression of tubal implantation from studies in humans and animal models, and highlight research questions in the field. DESIGN A search of the relevant literature using PubMed and other online tools. SETTING University-based preclinical and clinical research laboratories. PATIENT(S) Women with tubal ectopic pregnancy after Chlamydia trachomatis infection. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Critical review of the literature. RESULT(S) Chlamydia trachomatis infection poses a major threat to human reproduction. Biological and epidemiological evidence suggests that progression of Chlamydia infection causes intense and persistent inflammation, injury, and scarring in the fallopian tube, leading to a substantially increased risk of ectopic pregnancy and infertility. The main targets of Chlamydia infection are epithelial cells lining the mucosal surface, which play a central role in host immune responses and pathophysiology. Tubal phenotypes at the cellular level in mutant mice appear to reflect alterations in the balance between inflammatory mediator and factor deficiency. While studies in mice infected with Chlamydia muridarum have provided insight into potential inflammatory mediators linked to fallopian tube pathology, it is unclear how inflammation induced by Chlamydia infection prevents or retards normal tubal transport and causes embryo implantation in the fallopian tube. CONCLUSION(S) Given the similarities in the tubal physiology of humans and rodents, knockout mouse models can be used to study certain aspects of tubal functions, such as gamete transport and early embryo implantation. Elucidation of the exact molecular mechanisms of immune and inflammatory responses caused by Chlamydia infection in human fallopian tubal cells in vitro and understanding how Chlamydia infection affects tubal transport and implantation in animal studies in vivo may explain how Chlamydia trachomatis infection drives inflammation and develops the tubal pathology in women with tubal ectopic pregnancy.
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Affiliation(s)
- Ruijin Shao
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
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18
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Pulliainen AT, Dehio C. Persistence of Bartonella spp. stealth pathogens: from subclinical infections to vasoproliferative tumor formation. FEMS Microbiol Rev 2012; 36:563-99. [PMID: 22229763 DOI: 10.1111/j.1574-6976.2012.00324.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 12/13/2011] [Accepted: 12/13/2011] [Indexed: 01/11/2023] Open
Abstract
Bartonella spp. are facultative intracellular bacteria that typically cause a long-lasting intraerythrocytic bacteremia in their mammalian reservoir hosts, thereby favoring transmission by blood-sucking arthropods. In most cases, natural reservoir host infections are subclinical and the relapsing intraerythrocytic bacteremia may last weeks, months, or even years. In this review, we will follow the infection cycle of Bartonella spp. in a reservoir host, which typically starts with an intradermal inoculation of bacteria that are superficially scratched into the skin from arthropod feces and terminates with the pathogen exit by the blood-sucking arthropod. The current knowledge of bacterial countermeasures against mammalian immune response will be presented for each critical step of the pathogenesis. The prevailing models of the still-enigmatic primary niche and the anatomical location where bacteria reside, persist, and are periodically seeded into the bloodstream to cause the typical relapsing Bartonella spp. bacteremia will also be critically discussed. The review will end up with a discussion of the ability of Bartonella spp., namely Bartonella henselae, Bartonella quintana, and Bartonella bacilliformis, to induce tumor-like vascular deformations in humans having compromised immune response such as in patients with AIDS.
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19
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Sharma M, Machuy N, Böhme L, Karunakaran K, Mäurer AP, Meyer TF, Rudel T. HIF-1α is involved in mediating apoptosis resistance to Chlamydia trachomatis-infected cells. Cell Microbiol 2011; 13:1573-85. [PMID: 21824245 DOI: 10.1111/j.1462-5822.2011.01642.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chlamydiae are obligate intracellular Gram-negative bacteria that cause widespread diseases in humans. Due to the intimate association between bacterium and host, Chlamydia evolved various strategies to protect their host cell against death-inducing stimuli, allowing the bacterium to complete its development cycle. An RNA interference (RNAi)-based screen was used to identify host cell factors required for apoptosis resistance of human epithelial cells infected with Chlamydia trachomatis serovar L2. Among the 32 validated hits, the anti-apoptotic Bcl-2 family member Mcl-1 was identified as a target. Protein network analyses implicated the transcription factor hypoxia-induced factor 1 alpha (HIF-1α) to be central to the regulation of many of the identified targets. Further mechanistic investigations showed that HIF-1α was stabilized within the host cell cytoplasm during early infection time points, followed by its translocation to the nucleus and eventual transcriptional activation of Mcl-1. siRNA-mediated depletion of HIF-1α led to a drastic decrease in Mcl-1, rendering the cell sensitive to apoptosis induction. Taken together, our findings identify HIF-1α as responsible for upregulation of Mcl-1 and the maintenance of apoptosis resistance during Chlamydia infection.
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Affiliation(s)
- Manu Sharma
- Max Planck Institute for Infection Biology, Department of Molecular Biology, Charitéplatz 1, D-10117 Berlin, Germany
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20
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Srivastava P, Vardhan H, Bhengraj AR, Jha R, Singh LC, Salhan S, Mittal A. Azithromycin Treatment Modulates the Extracellular Signal-Regulated Kinase Mediated Pathway and Inhibits Inflammatory Cytokines and Chemokines in Epithelial Cells from Infertile Women with RecurrentChlamydia trachomatisInfection. DNA Cell Biol 2011; 30:545-54. [DOI: 10.1089/dna.2010.1167] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Pragya Srivastava
- Institute of Pathology, Indian Council of Medical Research, New Delhi, India
| | - Harsh Vardhan
- Institute of Pathology, Indian Council of Medical Research, New Delhi, India
| | | | - Rajneesh Jha
- Institute of Pathology, Indian Council of Medical Research, New Delhi, India
| | | | - Sudha Salhan
- Department of Gynecology and Obstetrics, Safdarjung Hospital, New Delhi, India
| | - Aruna Mittal
- Institute of Pathology, Indian Council of Medical Research, New Delhi, India
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21
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Karunakaran K, Mehlitz A, Rudel T. Evolutionary conservation of infection-induced cell death inhibition among Chlamydiales. PLoS One 2011; 6:e22528. [PMID: 21799887 PMCID: PMC3142178 DOI: 10.1371/journal.pone.0022528] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Accepted: 06/23/2011] [Indexed: 11/19/2022] Open
Abstract
Control of host cell death is of paramount importance for the survival and replication of obligate intracellular bacteria. Among these, human pathogenic Chlamydia induces the inhibition of apoptosis in a variety of different host cells by directly interfering with cell death signaling. However, the evolutionary conservation of cell death regulation has not been investigated in the order Chlamydiales, which also includes Chlamydia-like organisms with a broader host spectrum. Here, we investigated the apoptotic response of human cells infected with the Chlamydia-like organism Simkania negevensis (Sn). Simkania infected cells exhibited strong resistance to apoptosis induced by intrinsic stress or by the activation of cell death receptors. Apoptotic signaling was blocked upstream of mitochondria since Bax translocation, Bax and Bak oligomerisation and cytochrome c release were absent in these cells. Infected cells turned on pro-survival pathways like cellular Inhibitor of Apoptosis Protein 2 (cIAP-2) and the Akt/PI3K pathway. Blocking any of these inhibitory pathways sensitized infected host cell towards apoptosis induction, demonstrating their role in infection-induced apoptosis resistance. Our data support the hypothesis of evolutionary conserved signaling pathways to apoptosis resistance as common denominators in the order Chlamydiales.
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Affiliation(s)
- Karthika Karunakaran
- Department of Microbiology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Adrian Mehlitz
- Department of Microbiology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Thomas Rudel
- Department of Microbiology, Biocenter, University of Würzburg, Würzburg, Germany
- * E-mail:
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22
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Deniset JF, Pierce GN. Possibilities for therapeutic interventions in disrupting Chlamydophila pneumoniae involvement in atherosclerosis. Fundam Clin Pharmacol 2011; 24:607-17. [PMID: 20653790 DOI: 10.1111/j.1472-8206.2010.00863.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Strong sero-epidemiologic, pathologic, and experimental evidence suggests that Chlamydophila pneumoniae (Cpn) infection may play a causative role in the development of atherosclerosis. Cpn is an obligate intracellular gram-negative bacterium that is responsible for 10% of cases of community-acquired pneumonia. In addition to its presence in the respiratory tract, live Cpn has been found within atherosclerotic plaques. Experimental findings have established Cpn's ability to infect vascular cells and elicit important atherogenic responses. Furthermore, Cpn infection can promote atherosclerotic development in different animal models. To date however, large-scale antibiotic clinical trials have not been effective in preventing major cardiovascular events. It is becoming apparent that Cpn undergoes a persistent state of infection, which is refractory to current chlamydial antibiotics. New treatment strategies that are effective toward acute and persistent forms of Cpn infection are needed in order to effectively eradicate the bacterium within the vascular wall. Possible therapeutics targets include Cpn-specific proteins and machinery directly involved in their survival, replication and maintenance. Alternatively, selectively targeting host cell pathways and machinery required for Cpn's actions in vascular cells also represent potential treatment strategies for atherosclerosis.
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Affiliation(s)
- Justin F Deniset
- Department of Physiology, Faculties of Medicine and Pharmacy, Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Manitoba, Canada
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23
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Interactions between bacterial pathogens and mitochondrial cell death pathways. Nat Rev Microbiol 2010; 8:693-705. [PMID: 20818415 DOI: 10.1038/nrmicro2421] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The modulation of host cell death pathways by bacteria has been recognized as a major pathogenicity mechanism. Among other strategies, bacterial pathogens can hijack the cell death machinery of host cells by influencing the signalling pathways that converge on the mitochondria. In particular, many bacterial proteins have evolved to interact in a highly specific manner with host mitochondria, thereby modulating the decision between cell life and death. In this Review, we explore the intimate interactions between bacterial pathogens and mitochondrial cell death pathways.
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24
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Jha R, Vardhan H, Bas S, Salhan S, Mittal A. Chlamydia trachomatis heat shock proteins 60 and 10 induce apoptosis in endocervical epithelial cells. Inflamm Res 2010; 60:69-78. [DOI: 10.1007/s00011-010-0237-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 07/18/2010] [Indexed: 11/30/2022] Open
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25
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Böhme L, Albrecht M, Riede O, Rudel T. Chlamydia trachomatis-infected host cells resist dsRNA-induced apoptosis. Cell Microbiol 2010; 12:1340-51. [PMID: 20482554 DOI: 10.1111/j.1462-5822.2010.01473.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Human pathogenic Chlamydia trachomatis have evolved sophisticated mechanisms to manipulate host cell signalling pathways in order to prevent apoptosis. We show here that host cells infected with C. trachomatis resist apoptosis induced by polyI:C, a synthetic double-stranded RNA that mimics viral infections. Infected cells displayed significantly reduced levels of PARP cleavage, caspase-3 activation and a decrease in the TUNEL positive population in the presence of polyI:C. Interestingly, the chlamydial block of apoptosis was upstream of the initiator caspase-8. Processing of caspase-8 was reduced in infected cells and coincided with a decrease in Bid truncation and downstream caspase-9 cleavage. Moreover, the enzymatic activity of caspase-8, measured by a luminescent substrate, was significantly reduced in infected cells. Caspase-8 inhibition by Chlamydia was dependent on cFlip as knock-down of cFlip decreased the chlamydial block of caspase-8 activation and consequently reduced apoptosis inhibition. Our data implicate that chlamydial infection interferes with the host cell's response to viral infections and thereby influences the fate of the cell.
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Affiliation(s)
- Linda Böhme
- Biocenter, University of Würzburg, 97074 Würzburg, Germany
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26
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Prakash H, Albrecht M, Becker D, Kuhlmann T, Rudel T. Deficiency of XIAP leads to sensitization for Chlamydophila pneumoniae pulmonary infection and dysregulation of innate immune response in mice. J Biol Chem 2010; 285:20291-302. [PMID: 20427267 DOI: 10.1074/jbc.m109.096297] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Obligate intracellular Chlamydophila pneumoniae induce apoptosis resistance in host cells to escape eradication by immune effector cells. Apoptosis resistance depends on the increased expression and stabilization of cellular inhibitor of apoptosis proteins (cIAPs) and X-linked inhibitor of apoptosis protein (XIAP). Here we investigated the role of XIAP in experimental pulmonary infection of mice with C. pneumoniae. XIAP knock out (KO) mice were sensitized for C. pneumoniae infection compared with wild type mice. XIAP was involved in lipopolysaccharide (LPS)-induced production of nitric oxide (NO) and endotoxin shock. Hyper-secretion of tumor necrosis factor-alpha and lower NO in LPS-treated KO mouse macrophages revealed its regulatory role in inflammatory responses. Unexpectedly, activating stimuli like LPS, tumor necrosis factor-alpha, or interferon-gamma very efficiently induced apoptotic cell death in KO macrophages but not in wild type macrophages. Cell survival transcription factor nuclear factor kappaB (NF-kappaB) p65 levels were reduced in lungs and pulmonary macrophages of infected KO mice. Furthermore, a reduced CD8 T cell population and their increased sensitivity for concanavalin A and chlamydial HSP60 stimulation revealed a defect in CD8 T cells in XIAP KO mice. These data demonstrated a role of XIAP for the integrity of both innate and cellular immune responses during C. pneumoniae infection.
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Affiliation(s)
- Hridayesh Prakash
- Department of Molecular Biology, Max-Planck-Institute for Infection Biology, Charitéplatz 1, D-10117 Berlin, Germany
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27
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Kern JM, Maass V, Maass M. Molecular pathogenesis of chronic Chlamydia pneumoniae infection: a brief overview. Clin Microbiol Infect 2009; 15:36-41. [PMID: 19220338 DOI: 10.1111/j.1469-0691.2008.02631.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Owing to its unique host cell-dependent development cycle, Chlamydia pneumoniae occupies an intracellular niche that enables the bacterium to survive and to multiply, secluded from both the extracellular and the cytoplasmic environments. Within its separate chlamydial inclusion, it is able to genetically switch between a replicative and a persisting non-replicative state, linking the pathogen to acute as well as chronic diseases. Although its role in acute respiratory infection has been established, a potential link between chronic vascular infection with C. pneumoniae and the development of atherosclerosis remains enigmatic, in particular because chronic chlamydial infection cannot be eradicated by antibiotics. C. pneumoniae has developed numerous mechanisms to establish an adequate growth milieu involving the type III secretion-mediated release of chlamydial effector proteins that interact with cellular structures and reprogram host cell regulatory pathways. This brief overview of these pathomechanisms focuses on chronic vascular infection.
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Affiliation(s)
- J M Kern
- Institute of Medical Microbiology, Hygiene and Infectious Diseases, University Hospital Salzburg, Salzburg, Austria
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28
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cIAP-1 controls innate immunity to C. pneumoniae pulmonary infection. PLoS One 2009; 4:e6519. [PMID: 19657383 PMCID: PMC2716518 DOI: 10.1371/journal.pone.0006519] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 06/08/2009] [Indexed: 01/14/2023] Open
Abstract
The resistance of epithelial cells infected with Chlamydophila pneumoniae for apoptosis has been attributed to the induced expression and increased stability of anti-apoptotic proteins called inhibitor of apoptosis proteins (IAPs). The significance of cellular inhibitor of apoptosis protein-1 (cIAP-1) in C. pneumoniae pulmonary infection and innate immune response was investigated in cIAP-1 knockout (KO) mice using a novel non-invasive intra-tracheal infection method. In contrast to wildtype, cIAP-1 knockout mice failed to clear the infection from their lungs. Wildtype mice responded to infection with a strong inflammatory response in the lung. In contrast, the recruitment of macrophages was reduced in cIAP-1 KO mice compared to wildtype mice. The concentration of Interferon gamma (IFN-γ) was increased whereas that of Tumor Necrosis Factor (TNF-α) was reduced in the lungs of infected cIAP-1 KO mice compared to infected wildtype mice. Ex vivo experiments on mouse peritoneal macrophages and splenocytes revealed that cIAP-1 is required for innate immune responses of these cells. Our findings thus suggest a new immunoregulatory role of cIAP-1 in the course of bacterial infection.
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29
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Neisseria gonorrhoeae infection protects human endocervical epithelial cells from apoptosis via expression of host antiapoptotic proteins. Infect Immun 2009; 77:3602-10. [PMID: 19546192 DOI: 10.1128/iai.01366-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Several microbial pathogens can modulate the host apoptotic response to infection, which may contribute to immune evasion. Various studies have reported that infection with the sexually transmitted disease pathogen Neisseria gonorrhoeae can either inhibit or induce apoptosis. N. gonorrhoeae infection initiates at the mucosal epithelium, and in women, cells from the ectocervix and endocervix are among the first host cells encountered by this pathogen. In this study, we defined the antiapoptotic effect of N. gonorrhoeae infection in human endocervical epithelial cells (End/E6E7 cells). We first established that N. gonorrhoeae strain FA1090B failed to induce cell death in End/E6E7 cells. Subsequently, we demonstrated that stimulation with N. gonorrhoeae protected these cells from staurosporine (STS)-induced apoptosis. Importantly, only End/E6E7 cells incubated with live bacteria and in direct association with N. gonorrhoeae were protected from STS-induced apoptosis, while heat-killed and antibiotic-killed bacteria failed to induce protection. Stimulation of End/E6E7 cells with live N. gonorrhoeae induced NF-kappaB activation and resulted in increased gene expression of the NF-kappaB-regulated antiapoptotic genes bfl-1, cIAP-2, and c-FLIP. Furthermore, cIAP-2 protein levels also increased in End/E6E7 cells incubated with gonococci. Collectively, our results indicate that the antiapoptotic effect of N. gonorrhoeae in human endocervical epithelial cells results from live infection via expression of host antiapoptotic proteins. Securing an intracellular niche through the inhibition of apoptosis may be an important mechanism utilized by N. gonorrhoeae for microbial survival and immune evasion in cervical epithelial cells.
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30
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Ying S, Pettengill M, Latham ER, Walch A, Ojcius DM, Häcker G. Premature apoptosis of Chlamydia-infected cells disrupts chlamydial development. J Infect Dis 2009; 198:1536-44. [PMID: 18821848 DOI: 10.1086/592755] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The obligate intracellular development of Chlamydia suggests that the bacteria should be vulnerable to premature host cell apoptosis, but because Chlamydia-infected cells are apoptosis resistant, this has never been able to be tested. We have devised a system to circumvent the apoptotic block imposed by chlamydial infection. When the proapoptotic protein Bim(S) was experimentally induced, epithelial cells underwent apoptosis that was not blocked by chlamydial infection. Apoptosis during the developmental cycle prevented the generation of infectious bacteria and caused transcriptional changes of bacterial genes and loss of intracellular ATP. Intriguingly, although apoptosis resulted in destruction of host cell structures and of the Chlamydia inclusion, and prevented generation of elementary bodies, Bim(S) induction in the presence of a caspase inhibitor allowed differentiation into morphologically normal but noninfectious elementary bodies. These data show that chlamydial infection renders host cells apoptosis resistant at a premitochondrial step and demonstrate the consequences of premature apoptosis for development of the bacteria.
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Affiliation(s)
- Songmin Ying
- Institute for Medical Microbiology, Immunology and Hygiene, Technical University Munich, Germany
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31
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Liu X, Togo S, Al-Mugotir M, Kim H, Fang Q, Kobayashi T, Wang X, Mao L, Bitterman P, Rennard S. NF-kappaB mediates the survival of human bronchial epithelial cells exposed to cigarette smoke extract. Respir Res 2008; 9:66. [PMID: 18811964 PMCID: PMC2567966 DOI: 10.1186/1465-9921-9-66] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 09/23/2008] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND We have previously reported that low concentrations of cigarette smoke extract induce DNA damage without leading to apoptosis or necrosis in human bronchial epithelial cells (HBECs), and that IL-6/STAT3 signaling contributes to the cell survival. Since NF-kappaB is also involved in regulating apoptosis and cell survival, the current study was designed to investigate the role of NF-kappaB in mediating cell survival in response to cigarette smoke exposure in HBECs. METHODS Both the pharmacologic inhibitor of NF-kappaB, curcumin, and RNA interference targeting p65 were used to block NF-kappaB signaling in HBECs. Apoptosis and cell survival were then assessed by various methods including COMET assay, LIVE/DEAD Cytotoxicity/Viability assay and colony formation assay. RESULTS Cigarette smoke extract (CSE) caused DNA damage and cell cycle arrest in S phase without leading to apoptosis in HBECs as evidenced by TUNEL assay, COMET assay and DNA content assay. CSE stimulated NF-kappaB -DNA binding activity and up-regulated Bcl-XL protein in HBECs. Inhibition of NF-kappaB by the pharmacologic inhibitor curcumin (20 microM) or suppression of p65 by siRNA resulted in a significant increase in cell death in response to cigarette smoke exposure. Furthermore, cells lacking p65 were incapable of forming cellular colonies when these cells were exposed to CSE, while they behaved normally in the regular culture medium. CONCLUSION The current study demonstrates that CSE activates NF-kappaB and up-regulates Bcl-XL through NF-kB activation in HBECs, and that CSE induces cell death in cells lacking p65. These results suggest that activation of NF-kappaB regulates cell survival following DNA damage by cigarette smoke in human bronchial epithelial cells.
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Affiliation(s)
- Xiangde Liu
- Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Shinsaku Togo
- Juntendo University, School of Medicine, Tokyo, Japan
| | - Mona Al-Mugotir
- Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Huijung Kim
- Won Kwang University, Kunpo Medical Center, Seoul, Republic of Korea
| | - QiuHong Fang
- Beijing Shijitan Hospital, Peking University, Beijing, PR China
| | - Tetsu Kobayashi
- Mie University of Graduate School of Medicine, Tsu City, Japan
| | - XingQi Wang
- Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Lijun Mao
- The 3Hospital of Peking University, Beijing, PR China
| | | | - Stephen Rennard
- Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
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Rajalingam K, Sharma M, Lohmann C, Oswald M, Thieck O, Froelich CJ, Rudel T. Mcl-1 is a key regulator of apoptosis resistance in Chlamydia trachomatis-infected cells. PLoS One 2008; 3:e3102. [PMID: 18769617 PMCID: PMC2518856 DOI: 10.1371/journal.pone.0003102] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Accepted: 07/29/2008] [Indexed: 02/04/2023] Open
Abstract
Chlamydia are obligate intracellular bacteria that cause variety of human diseases. Host cells infected with Chlamydia are protected against many different apoptotic stimuli. The induction of apoptosis resistance is thought to be an important immune escape mechanism allowing Chlamydia to replicate inside the host cell. Infection with C. trachomatis activates the Raf/MEK/ERK pathway and the PI3K/AKT pathway. Here we show that inhibition of these two pathways by chemical inhibitors sensitized C. trachomatis infected cells to granzyme B-mediated cell death. Infection leads to the Raf/MEK/ERK-mediated up-regulation and PI3K-dependent stabilization of the anti-apoptotic Bcl-2 family member Mcl-1. Consistently, interfering with Mcl-1 up-regulation sensitized infected cells for apoptosis induced via the TNF receptor, DNA damage, granzyme B and stress. Our data suggest that Mcl-1 up-regulation is primarily required to maintain apoptosis resistance in C. trachomatis-infected cells.
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Affiliation(s)
- Krishnaraj Rajalingam
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Manu Sharma
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Christine Lohmann
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Monique Oswald
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Oliver Thieck
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | | | - Thomas Rudel
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
- * E-mail:
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Appelt DM, Roupas MR, Way DS, Bell MG, Albert EV, Hammond CJ, Balin BJ. Inhibition of apoptosis in neuronal cells infected with Chlamydophila (Chlamydia) pneumoniae. BMC Neurosci 2008; 9:13. [PMID: 18218130 PMCID: PMC2266938 DOI: 10.1186/1471-2202-9-13] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Accepted: 01/24/2008] [Indexed: 12/29/2022] Open
Abstract
Background Chlamydophila (Chlamydia) pneumoniae is an intracellular bacterium that has been identified within cells in areas of neuropathology found in Alzheimer disease (AD), including endothelia, glia, and neurons. Depending on the cell type of the host, infection by C. pneumoniae has been shown to influence apoptotic pathways in both pro- and anti-apoptotic fashions. We have hypothesized that persistent chlamydial infection of neurons may be an important mediator of the characteristic neuropathology observed in AD brains. Chronic and/or persistent infection of neuronal cells with C. pneumoniae in the AD brain may affect apoptosis in cells containing chlamydial inclusions. Results SK-N-MC neuroblastoma cells were infected with the respiratory strain of C. pneumoniae, AR39 at an MOI of 1. Following infection, the cells were either untreated or treated with staurosporine and then examined for apoptosis by labeling for nuclear fragmentation, caspase activity, and membrane inversion as indicated by annexin V staining. C. pneumoniae infection was maintained through 10 days post-infection. At 3 and 10 days post-infection, the infected cell cultures appeared to inhibit or were resistant to the apoptotic process when induced by staurosporine. This inhibition was demonstrated quantitatively by nuclear profile counts and caspase 3/7 activity measurements. Conclusion These data suggest that C. pneumoniae can sustain a chronic infection in neuronal cells by interfering with apoptosis, which may contribute to chronic inflammation in the AD brain.
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Affiliation(s)
- Denah M Appelt
- Department of Neuroscience, Physiology & Pharmacology, Philadelphia College of Osteopathic Medicine, Philadelphia, USA.
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Paland N, Böhme L, Gurumurthy RK, Mäurer A, Szczepek AJ, Rudel T. Reduced display of tumor necrosis factor receptor I at the host cell surface supports infection with Chlamydia trachomatis. J Biol Chem 2007; 283:6438-48. [PMID: 18167350 DOI: 10.1074/jbc.m708422200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The obligate intracellular human pathogenic bacterium Chlamydia trachomatis has evolved multiple mechanisms to circumvent the host immune system. Infected cells exhibit a profound resistance to the induction of apoptosis and down-regulate the expression of major histocompatibility complex class I and class II molecules to evade the cytotoxic effect of effector immune cells. Here we demonstrate the down-regulation of tumor necrosis factor receptor 1 (TNFR1) on the surface of infected cells. Interestingly, other members of the TNFR family such as TNFR2 and CD95 (Fas/Apo-1) were not modulated during infection, suggesting a selective mechanism underlying surface reduction of TNFR1. The observed effect was not due to reduced expression since the overall amount of TNFR1 protein was increased in infected cells. TNFR1 accumulated at the chlamydial inclusion and was shed by the infected cell into the culture supernatant. Receptor shedding depended on the infection-induced activation of the MEK-ERK pathway and the metalloproteinase TACE (TNFalpha converting enzyme). Our results point to a new function of TNFR1 modulation by C. trachomatis in controlling inflammatory signals during infection.
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Affiliation(s)
- Nicole Paland
- Research Group for Molecular Infection and Tumor Biology, Max Planck Institute for Infection Biology, Charitéplatz 1, Berlin, Germany
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35
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Ying S, Christian JG, Paschen SA, Häcker G. Chlamydia trachomatis can protect host cells against apoptosis in the absence of cellular Inhibitor of Apoptosis Proteins and Mcl-1. Microbes Infect 2007; 10:97-101. [PMID: 18069034 DOI: 10.1016/j.micinf.2007.10.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 10/05/2007] [Accepted: 10/08/2007] [Indexed: 11/28/2022]
Abstract
Infection with Chlamydia protects mammalian host cells against apoptosis. Hypotheses have been proposed to explain this molecularly, including the up-regulation of host anti-apoptotic proteins such as cellular Inhibitor of Apoptosis Protein (IAP) 2 and the Bcl-2 protein Mcl-1. To test for the importance of these proteins, we used mouse embryonic fibroblasts from gene-targeted mice that were deficient in cIAP1, cIAP2, cIAP1/cIAP2, XIAP, or Mcl-1. Infection with Chlamydia trachomatis protected all cells equally well against apoptosis, which was induced either with tumour necrosis factor/cycloheximide (IAP-knock-out cells) or staurosporine (Mcl-1-knock-out). Therefore, these cellular anti-apoptotic proteins are not essential for apoptosis-protection by C. trachomatis.
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Affiliation(s)
- Songmin Ying
- Institute for Medical Microbiology, Immunology and Hygiene, Technical University Munich, Trogerstrasse 30, D-81675 Munich, Germany
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36
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Papenfort K, Pfeiffer V, Mika F, Lucchini S, Hinton JCD, Vogel J. SigmaE-dependent small RNAs of Salmonella respond to membrane stress by accelerating global omp mRNA decay. Mol Microbiol 2007; 62:1674-88. [PMID: 17427289 PMCID: PMC1804206 DOI: 10.1111/j.1365-2958.2006.05524.x] [Citation(s) in RCA: 280] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bacterial envelope stress response (ESR) is triggered by the accumulation of misfolded outer membrane proteins (OMPs) upon envelope damage or excessive OMP synthesis, and is mediated by the alternative sigma factor, sigmaE. Activation of the GE pathway causes a rapid downregulation of major omp mRNAs, which prevents further build-up of unassembled OMPs and liberates the translocation and folding apparatus under conditions that require envelope remodelling. The factors that facilitate the rapid removal of the unusually stable omp mRNAs in the ESR were previously unknown. We report that in Salmonella the ESR relies upon two highly conserved, sigmaE-controlled small non-coding RNAs, RybB and MicA. By using a transcriptomic approach and kinetic analyses of target mRNA decay in vivo, RybB was identified as the factor that selectively accelerates the decay of multiple major omp mRNAs upon induction of the ESR, while MicA is proposed to facilitate rapid decay of the single ompA mRNA. In unstressed bacterial cells, the two oE-dependent small RNAs function within a surveillance loop to maintain envelope homeostasis and to achieve autoregulation of oE.
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Affiliation(s)
- Kai Papenfort
- Max Planck Institute for Infection BiologyCharitéplatz 1, 10117 Berlin, Germany
| | - Verena Pfeiffer
- Max Planck Institute for Infection BiologyCharitéplatz 1, 10117 Berlin, Germany
| | - Franziska Mika
- Max Planck Institute for Infection BiologyCharitéplatz 1, 10117 Berlin, Germany
| | - Sacha Lucchini
- Institute of Food Research, Norwich Research ParkNorwich, NR4 7UA, UK
| | - Jay C D Hinton
- Institute of Food Research, Norwich Research ParkNorwich, NR4 7UA, UK
- *For correspondence. E-mail ; Tel. (+49) 30 28460 265; Fax (+49) 30 28460 244; E-mail ; Tel. (+44) 1603 255352; Fax (+44) 1603 255288
| | - Jörg Vogel
- Max Planck Institute for Infection BiologyCharitéplatz 1, 10117 Berlin, Germany
- *For correspondence. E-mail ; Tel. (+49) 30 28460 265; Fax (+49) 30 28460 244; E-mail ; Tel. (+44) 1603 255352; Fax (+44) 1603 255288
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Ying S, Pettengill M, Ojcius DM, Häcker G. Host-Cell Survival and Death During Chlamydia Infection. CURRENT IMMUNOLOGY REVIEWS 2007; 3:31-40. [PMID: 18843378 PMCID: PMC2562443 DOI: 10.2174/157339507779802179] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Different Chlamydia trachomatis strains are responsible for prevalent bacterial sexually-transmitted disease and represent the leading cause of preventable blindness worldwide. Factors that predispose individuals to disease and mechanisms by which chlamydiae cause inflammation and tissue damage remain unclear. Results from recent studies indicate that prolonged survival and subsequent death of infected cells and their effect on immune effector cells during chlamydial infection may be important in determining the outcome. Survival of infected cells is favored at early times of infection through inhibition of the mitochondrial pathway of apoptosis. Death at later times displays features of both apoptosis and necrosis, but pro-apoptotic caspases are not involved. Most studies on chlamydial modulation of host-cell death until now have been performed in cell lines. The consequences for pathogenesis and the immune response will require animal models of chlamydial infection, preferably mice with targeted deletions of genes that play a role in cell survival and death.
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Affiliation(s)
- Songmin Ying
- Institute for Medical Microbiology, Technische Universität München, D-81675 Munich, Germany
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Rajalingam K, Sharma M, Paland N, Hurwitz R, Thieck O, Oswald M, Machuy N, Rudel T. IAP-IAP complexes required for apoptosis resistance of C. trachomatis-infected cells. PLoS Pathog 2006; 2:e114. [PMID: 17069460 PMCID: PMC1626104 DOI: 10.1371/journal.ppat.0020114] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Accepted: 09/19/2006] [Indexed: 11/19/2022] Open
Abstract
Host cells infected with obligate intracellular bacteria Chlamydia trachomatis are profoundly resistant to diverse apoptotic stimuli. The molecular mechanisms underlying the block in apoptotic signaling of infected cells is not well understood. Here we investigated the molecular mechanism by which apoptosis induced via the tumor necrosis factor (TNF) receptor is prevented in infected epithelial cells. Infection with C. trachomatis leads to the up-regulation of cellular inhibitor of apoptosis (cIAP)-2, and interfering with cIAP-2 up-regulation sensitized infected cells for TNF-induced apoptosis. Interestingly, besides cIAP-2, cIAP-1 and X-linked IAP, although not differentially regulated by infection, are required to maintain apoptosis resistance in infected cells. We detected that IAPs are constitutively organized in heteromeric complexes and small interfering RNA-mediated silencing of one of these IAPs affects the stability of another IAP. In particular, the stability of cIAP-2 is modulated by the presence of X-linked IAP and their interaction is stabilized in infected cells. Our observations suggest that IAPs are functional and stable as heteromers, a thus far undiscovered mechanism of IAP regulation and its role in modulation of apoptosis.
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Affiliation(s)
- Krishnaraj Rajalingam
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Manu Sharma
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Nicole Paland
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Robert Hurwitz
- Biochemistry/Protein Purification Core Facility, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Oliver Thieck
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Monique Oswald
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Nikolaus Machuy
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Thomas Rudel
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
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