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Hu Q, Wang S, Zhang W, Qu J, Liu GH. Unraveling brain aging through the lens of oral microbiota. Neural Regen Res 2025; 20:1930-1943. [PMID: 38993126 DOI: 10.4103/nrr.nrr-d-23-01761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 05/31/2024] [Indexed: 07/13/2024] Open
Abstract
The oral cavity is a complex physiological community encompassing a wide range of microorganisms. Dysbiosis of oral microbiota can lead to various oral infectious diseases, such as periodontitis and tooth decay, and even affect systemic health, including brain aging and neurodegenerative diseases. Recent studies have highlighted how oral microbes might be involved in brain aging and neurodegeneration, indicating potential avenues for intervention strategies. In this review, we summarize clinical evidence demonstrating a link between oral microbes/oral infectious diseases and brain aging/neurodegenerative diseases, and dissect potential mechanisms by which oral microbes contribute to brain aging and neurodegeneration. We also highlight advances in therapeutic development grounded in the realm of oral microbes, with the goal of advancing brain health and promoting healthy aging.
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Affiliation(s)
- Qinchao Hu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Si Wang
- Advanced Innovation Center for Human Brain Protection and National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital, Capital Medical University, Beijing, China
- Aging Translational Medicine Center, International Center for Aging and Cancer, Beijing Municipal Geriatric Medical Research Center, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Weiqi Zhang
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Aging Biomarker Consortium, Beijing, China
| | - Jing Qu
- University of Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Aging Biomarker Consortium, Beijing, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
| | - Guang-Hui Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Advanced Innovation Center for Human Brain Protection and National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital, Capital Medical University, Beijing, China
- Aging Translational Medicine Center, International Center for Aging and Cancer, Beijing Municipal Geriatric Medical Research Center, Xuanwu Hospital, Capital Medical University, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Aging Biomarker Consortium, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
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2
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Butler CA, Ciccotosto GD, Rygh N, Bijlsma E, Dashper SG, Brown AC. Bacterial Membrane Vesicles: The Missing Link Between Bacterial Infection and Alzheimer Disease. J Infect Dis 2024; 230:S87-S94. [PMID: 39255395 PMCID: PMC11385588 DOI: 10.1093/infdis/jiae228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 04/28/2024] [Indexed: 09/12/2024] Open
Abstract
Periodontitis is a common chronic inflammatory disease, affecting approximately 19% of the global adult population. A relationship between periodontal disease and Alzheimer disease has long been recognized, and recent evidence has been uncovered to link these 2 diseases mechanistically. Periodontitis is caused by dysbiosis in the subgingival plaque microbiome, with a pronounced shift in the oral microbiota from one consisting primarily of Gram-positive aerobic bacteria to one predominated by Gram-negative anaerobes, such as Porphyromonas gingivalis. A common phenomenon shared by all bacteria is the release of membrane vesicles to facilitate biomolecule delivery across long distances. In particular, the vesicles released by P gingivalis and other oral pathogens have been found to transport bacterial components across the blood-brain barrier, initiating the physiologic changes involved in Alzheimer disease. In this review, we summarize recent data that support the relationship between vesicles secreted by periodontal pathogens to Alzheimer disease pathology.
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Affiliation(s)
| | | | - Nathaniel Rygh
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania, USA
| | - Elly Bijlsma
- Melbourne Dental School, The University of Melbourne, Australia
| | | | - Angela C Brown
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania, USA
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3
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Ciccotosto GD, Mohammed AI, Paolini R, Bijlsma E, Toulson S, Holden J, Reynolds EC, Dashper SG, Butler CA. Chronic Oral Inoculation of Porphyromonas gingivalis and Treponema denticola Induce Different Brain Pathologies in a Mouse Model of Alzheimer Disease. J Infect Dis 2024; 230:S109-S116. [PMID: 39255392 DOI: 10.1093/infdis/jiae286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2024] Open
Abstract
Periodontitis is a chronic inflammatory disease driven by dysbiosis in subgingival microbial communities leading to increased abundance of a limited number of pathobionts, including Porphyromonas gingivalis and Treponema denticola. Oral health, particularly periodontitis, is a modifiable risk factor for Alzheimer disease (AD) pathogenesis, with components of both these bacteria identified in postmortem brains of persons with AD. Repeated oral inoculation of mice with P. gingivalis results in brain infiltration of bacterial products, increased inflammation, and induction of AD-like biomarkers. P. gingivalis displays synergistic virulence with T. denticola during periodontitis. The aim of the current study was to determine the ability of P. gingivalis and T. denticola, grown in physiologically relevant conditions, individually and in combination, to induce AD-like pathology following chronic oral inoculation of female mice over 12 weeks. P. gingivalis alone significantly increased all 7 brain pathologies examined: neuronal damage, activation of astrocytes and microglia, expression of inflammatory cytokines interleukin 1β (IL-1β) and interleukin 6 and production of amyloid-β plaques and hyperphosphorylated tau, in the hippocampus, cortex and midbrain, compared to control mice. T. denticola alone significantly increased neuronal damage, activation of astrocytes and microglia, and expression of IL-1β, in the hippocampus, cortex and midbrain, compared to control mice. Coinoculation of P. gingivalis with T. denticola significantly increased activation of astrocytes and microglia in the hippocampus, cortex and midbrain, and increased production of hyperphosphorylated tau and IL-1β in the hippocampus only. The host brain response elicited by oral coinoculation was less than that elicited by each bacterium, suggesting coinoculation was less pathogenic.
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Affiliation(s)
| | - Ali I Mohammed
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - Rita Paolini
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - Elly Bijlsma
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - Su Toulson
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - James Holden
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - Eric C Reynolds
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - Stuart G Dashper
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
| | - Catherine A Butler
- Melbourne Dental School, The University of Melbourne, Melbourne, Australia
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4
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Zhao M, Wang Y, Shen Y, Wei C, Zhang G, Sun L. A review of the roles of pathogens in Alzheimer's disease. Front Neurosci 2024; 18:1439055. [PMID: 39224577 PMCID: PMC11366636 DOI: 10.3389/fnins.2024.1439055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2024] [Accepted: 08/01/2024] [Indexed: 09/04/2024] Open
Abstract
Alzheimer's disease (AD) is one of the leading causes of dementia and is characterized by memory loss, mental and behavioral abnormalities, and impaired ability to perform daily activities. Even as a global disease that threatens human health, effective treatments to slow the progression of AD have not been found, despite intensive research and significant investment. In recent years, the role of infections in the etiology of AD has sparked intense debate. Pathogens invade the central nervous system through a damaged blood-brain barrier or nerve trunk and disrupt the neuronal structure and function as well as homeostasis of the brain microenvironment through a series of molecular biological events. In this review, we summarize the various pathogens involved in AD pathology, discuss potential interactions between pathogens and AD, and provide an overview of the promising future of anti-pathogenic therapies for AD.
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Affiliation(s)
| | | | | | | | | | - Li Sun
- Department of Neurology, Neuroscience Center, The First Hospital of Jilin University, Jilin University, Changchun, China
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5
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Dai X, Liang R, Dai M, Li X, Zhao W. Smoking Impacts Alzheimer's Disease Progression Through Oral Microbiota Modulation. Mol Neurobiol 2024:10.1007/s12035-024-04241-1. [PMID: 38795302 DOI: 10.1007/s12035-024-04241-1] [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: 12/26/2023] [Accepted: 05/13/2024] [Indexed: 05/27/2024]
Abstract
Alzheimer's disease (AD) is an important public health challenge with a limited understanding of its pathogenesis. Smoking is a significant modifiable risk factor for AD progression, and its specific mechanism is often interpreted from a toxicological perspective. However, microbial infections also contribute to AD, with oral microbiota playing a crucial role in its progression. Notably, smoking alters the ecological structure and pathogenicity of the oral microbiota. Currently, there is no systematic review or summary of the relationship between these three factors; thus, understanding this association can help in the development of new treatments. This review summarizes the connections between smoking, AD, and oral microbiota from existing research. It also explores how smoking affects the occurrence and development of AD through oral microbiota, and examines treatments for oral microbiota that delay the progression of AD. Furthermore, this review emphasizes the potential of the oral microbiota to act as a biomarker for AD. Finally, it considers the feasibility of probiotics and oral antibacterial therapy to expand treatment methods for AD.
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Affiliation(s)
- Xingzhu Dai
- Department of Stomatology, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
- Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Rui Liang
- Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Manqiong Dai
- Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xiaoyu Li
- Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Wanghong Zhao
- Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, China.
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6
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Shen H, Jiang Y, Qiu C, Xie X, Zhang H, He Z, Song Z, Zhou W. Abnormal amyloid precursor protein processing in periodontal tissue in a murine model of periodontitis induced by Porphyromonas gingivalis. J Periodontal Res 2024; 59:395-407. [PMID: 38311599 DOI: 10.1111/jre.13224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 11/27/2023] [Accepted: 12/05/2023] [Indexed: 02/06/2024]
Abstract
OBJECTIVE The study aimed to investigate the change of amyloid precursor protein (APP) processing and amyloid β (Aβ) metabolites in linking periodontitis to Alzheimer's disease (AD). BACKGROUND Aβ is one of the main pathological features of AD, and few studies have discussed changes in its expression in peripheral tissues or analyzed the relationship between the peripheral imbalance of Aβ production and clearance. METHODS A murine model of periodontitis was established by oral infection with Porphyromonas gingivalis (P. gingivalis). Micro-computed tomography (Micro-CT) was used to observe the destruction of the alveolar bone. Nested quantitative polymerase chain reaction (qPCR) was used to measure small quantities of P.gingivalis DNA in different tissues. Behavioral experiments were performed to measure cognitive function in the mice. The mRNA levels of TNF-α, IL-6, IL-8, RANKL, OPG, APP695, APP751, APP770, and BACE1 in the gingival tissues or cortex were detected by RT-PCR. The levels of Aβ1-40 and Aβ1-42 in gingival crevicular fluid (GCF) and plasma were tested by ELISA. RESULTS P. gingivalis oral infection was found to cause alveolar bone resorption and impaired learning and memory. P.gingivalis DNA was detected in the gingiva, blood and cortex of the P.gingivalis group by nested qPCR (p < .05). The mRNA expression of TNF-α, IL-6, IL-8, RANKL/OPG, and BACE1 in the gingival tissue was significantly higher than that in the control group (p < .05). Similarly, upregulated mRNA levels of APP695 and APP770 were observed in the gingival tissuses and cortex of the P. gingivalis group (p < .05). The levels of Aβ1-40 and Aβ1-42 in the GCF and plasma of the P. gingivalis group were significantly higher than those in the control group (p < .05). CONCLUSION P. gingivalis can directly invade the brain via hematogenous infection. The invasion of P. gingivalis could trigger an immune response and lead to an imbalance between Aβ production and clearance in peripheral tissues, which may trigger an abnormal Aβ metabolite in the brain, resulting in the occurrence and development of AD.
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Affiliation(s)
- Hui Shen
- Department of Periodontology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
| | - Yiting Jiang
- Department of Periodontology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
| | - Che Qiu
- Department of Periodontology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
| | - Xinyi Xie
- Department of Periodontology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
| | - Huanyu Zhang
- Department of Periodontology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
| | - Zhiyan He
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
- Laboratory of Oral Microbiota and Systemic Diseases, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhongchen Song
- Department of Periodontology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
| | - Wei Zhou
- National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China
- Laboratory of Oral Microbiota and Systemic Diseases, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai, China
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7
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Li R, Wang J, Xiong W, Luo Y, Feng H, Zhou H, Peng Y, He Y, Ye Q. The oral-brain axis: can periodontal pathogens trigger the onset and progression of Alzheimer's disease? Front Microbiol 2024; 15:1358179. [PMID: 38362505 PMCID: PMC10868393 DOI: 10.3389/fmicb.2024.1358179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 01/18/2024] [Indexed: 02/17/2024] Open
Abstract
Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by a progressive cognitive decline. Sporadic AD, accounting for more than 95% of cases, may arise due to the influence of environmental factors. It was reported that periodontitis, a common oral ailment, shares several risk factors with AD, including advanced age, smoking, diabetes, and hypertension, among others. Periodontitis is an inflammatory disease triggered by dysbiosis of oral microorganisms, whereas Alzheimer's disease is characterized by neuroinflammation. Many studies have indicated that chronic inflammation can instigate brain AD-related pathologies, including amyloid-β plaques, Tau protein hyperphosphorylation, neuroinflammation, and neurodegeneration. The potential involvement of periodontal pathogens and/or their virulence factors in the onset and progression of AD by the oral-brain axis has garnered significant attention among researchers with ongoing investigations. This review has updated the periodontal pathogens potentially associated with AD, elucidating their impact on the central nervous system, immune response, and related pathological processes in the brain to provide valuable insights for future research on the oral-brain axis.
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Affiliation(s)
- Ruohan Li
- Center of Regenerative Medicine, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Junnan Wang
- Center of Regenerative Medicine, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Wei Xiong
- Center of Regenerative Medicine, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Yu Luo
- Center of Regenerative Medicine, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
- Department of Stomatology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Huixian Feng
- Department of Stomatology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Heng Zhou
- Center of Regenerative Medicine, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Youjian Peng
- Department of Stomatology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Yan He
- Institute of Regenerative and Translational Medicine, Tianyou Hospital, Wuhan University of Science and Technology, Wuhan, China
| | - Qingsong Ye
- Center of Regenerative Medicine, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
- Department of Stomatology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
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8
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Zürcher C, Humpel C. Saliva: a challenging human fluid to diagnose brain disorders with a focus on Alzheimer's disease. Neural Regen Res 2023; 18:2606-2610. [PMID: 37449596 DOI: 10.4103/1673-5374.373675] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023] Open
Abstract
Biomarkers are molecules of biological processes that help in both the diagnosis of human diseases and in follow-up assessments of therapeutic responses. Biomarkers can be measured in many human fluids, such as blood, cerebrospinal fluid, urine, and saliva. The -omics methods (genomics, RNomics, proteomics, and metabolomics) are useful at measuring thousands of markers in a small volume. Saliva is a human fluid that is easily accessible, without any ethical concerns. Yet, saliva remains unexplored in regard to many human disease biomarkers. In this review, we will give an overview on saliva and how it can be influenced by exogenous factors. As we focus on the potential use of saliva as a diagnostic tool in brain disorders (especially Alzheimer's disease), we will cover how saliva is linked to the brain. We will discuss that saliva is a heterogeneous human fluid, yet useful for the discovery of biomarkers in human disorders. However, a procedure and consensus that is controlled, validated, and standardized for the collection and processing of saliva is required, followed by a highly sensitive diagnostic approach.
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Affiliation(s)
- Christine Zürcher
- University Hospital for Restorative Dentistry and Periodontology, Medical University of Innsbruck, Innsbruck, Austria
| | - Christian Humpel
- Laboratory of Psychiatry & Experimental Alzheimer's Research, Department of Psychiatry I, Medical University of Innsbruck, Innsbruck, Austria
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Muok AR, Kurniyati K, Cassidy CK, Olsthoorn FA, Ortega DR, Mabrouk AS, Li C, Briegel A. A new class of protein sensor links spirochete pleomorphism, persistence, and chemotaxis. mBio 2023; 14:e0159823. [PMID: 37607060 PMCID: PMC10653840 DOI: 10.1128/mbio.01598-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 07/14/2023] [Indexed: 08/24/2023] Open
Abstract
IMPORTANCE A new class of bacterial protein sensors monitors intracellular levels of S-adenosylmethionine to modulate cell morphology, chemotaxis, and biofilm formation. Simultaneous regulation of these behaviors enables bacterial pathogens to survive within their niche. This sensor, exemplified by Treponema denticola CheWS, is anchored to the chemotaxis array and its sensor domain is located below the chemotaxis rings. This position may allow the sensor to directly interact with the chemotaxis histidine kinase CheA. Collectively, these data establish a critical role of CheWS in pathogenesis and further illustrate the impact of studying non-canonical chemotaxis proteins.
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Affiliation(s)
- A. R. Muok
- Institute of Biology, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - K. Kurniyati
- Department of Oral and Craniofacial Molecular Biology, Philips Research Institute for Oral Health, Virginia Commonwealth University, Richmond, Virginia, USA
| | - C. K. Cassidy
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, United Kingdom
| | - F. A. Olsthoorn
- Institute of Biology, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - D. R. Ortega
- Institute of Biology, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - A. Sidi Mabrouk
- Institute of Biology, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - C. Li
- Department of Oral and Craniofacial Molecular Biology, Philips Research Institute for Oral Health, Virginia Commonwealth University, Richmond, Virginia, USA
| | - A. Briegel
- Institute of Biology, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
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10
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Wan J, Fan H. Oral Microbiome and Alzheimer's Disease. Microorganisms 2023; 11:2550. [PMID: 37894208 PMCID: PMC10609607 DOI: 10.3390/microorganisms11102550] [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: 09/18/2023] [Revised: 10/06/2023] [Accepted: 10/12/2023] [Indexed: 10/29/2023] Open
Abstract
The accumulation of amyloid-beta plaques in the brain is a central pathological feature of Alzheimer's disease. It is believed that amyloid responses may be a result of the host immune response to pathogens in both the central nervous system and peripheral systems. Oral microbial dysbiosis is a chronic condition affecting more than 50% of older adults. Recent studies have linked oral microbial dysbiosis to a higher brain Aβ load and the development of Alzheimer's disease in humans. Moreover, the presence of an oral-derived and predominant microbiome has been identified in the brains of patients with Alzheimer's disease and other neurodegenerative diseases. Therefore, in this opinion article, we aim to provide a summary of studies on oral microbiomes that may contribute to the pathogenesis of the central nervous system in Alzheimer's disease.
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Affiliation(s)
- Jason Wan
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA;
- Charleston County School of the Arts High School, North Charleston, SC 29405, USA
| | - Hongkuan Fan
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA;
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11
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Ha JY, Seok J, Kim SJ, Jung HJ, Ryu KY, Nakamura M, Jang IS, Hong SH, Lee Y, Lee HJ. Periodontitis promotes bacterial extracellular vesicle-induced neuroinflammation in the brain and trigeminal ganglion. PLoS Pathog 2023; 19:e1011743. [PMID: 37871107 PMCID: PMC10621956 DOI: 10.1371/journal.ppat.1011743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 11/02/2023] [Accepted: 10/10/2023] [Indexed: 10/25/2023] Open
Abstract
Gram-negative bacteria derived extracellular vesicles (EVs), also known as outer membrane vesicles, have attracted significant attention due to their pathogenic roles in various inflammatory diseases. We recently demonstrated that EVs secreted by the periodontopathogen Aggregatibacter actinomycetemcomitans (Aa) can cross the blood-brain barrier (BBB) and that their extracellular RNA cargo can promote the secretion of proinflammatory cytokines, such as IL-6 and TNF-α, in the brain. To gain more insight into the relationship between periodontal disease (PD) and neuroinflammatory diseases, we investigated the effect of Aa EVs in a mouse model of ligature-induced PD. When EVs were administered through intragingival injection or EV-soaked gel, proinflammatory cytokines were strongly induced in the brains of PD mice. The use of TLR (Toll-like receptor)-reporter cell lines and MyD88 knockout mice confirmed that the increased release of cytokines was triggered by Aa EVs via TLR4 and TLR8 signaling pathways and their downstream MyD88 pathway. Furthermore, the injection of EVs through the epidermis and gingiva resulted in the direct retrograde transfer of Aa EVs from axon terminals to the cell bodies of trigeminal ganglion (TG) neurons and the subsequent activation of TG neurons. We also found that the Aa EVs changed the action potential of TG neurons. These findings suggest that EVs derived from periodontopathogens such as Aa might be involved in pathogenic pathways for neuroinflammatory diseases, neuropathic pain, and other systemic inflammatory symptoms as a comorbidity of periodontitis.
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Affiliation(s)
- Jae Yeong Ha
- Department of Microbiology and Immunology, School of Dentistry, Kyungpook National University, Daegu, Korea
- Craniofacial Nerve-Bone Network Research Center, Kyungpook National University, Daegu, Korea
| | - Jiwon Seok
- Department of Biochemistry, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Suk-Jeong Kim
- Department of Microbiology and Immunology, School of Dentistry, Kyungpook National University, Daegu, Korea
- Craniofacial Nerve-Bone Network Research Center, Kyungpook National University, Daegu, Korea
| | - Hye-Jin Jung
- Department of Biochemistry, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Ka-Young Ryu
- Craniofacial Nerve-Bone Network Research Center, Kyungpook National University, Daegu, Korea
- Department of Biochemistry, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Michiko Nakamura
- Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, Korea
- Brain Science & Engineering Institute, Kyungpook National University, Daegu, Korea
| | - Il-Sung Jang
- Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, Korea
- Brain Science & Engineering Institute, Kyungpook National University, Daegu, Korea
| | - Su-Hyung Hong
- Department of Microbiology and Immunology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Youngkyun Lee
- Craniofacial Nerve-Bone Network Research Center, Kyungpook National University, Daegu, Korea
- Department of Biochemistry, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Heon-Jin Lee
- Department of Microbiology and Immunology, School of Dentistry, Kyungpook National University, Daegu, Korea
- Craniofacial Nerve-Bone Network Research Center, Kyungpook National University, Daegu, Korea
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12
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Catumbela CSG, Giridharan VV, Barichello T, Morales R. Clinical evidence of human pathogens implicated in Alzheimer's disease pathology and the therapeutic efficacy of antimicrobials: an overview. Transl Neurodegener 2023; 12:37. [PMID: 37496074 PMCID: PMC10369764 DOI: 10.1186/s40035-023-00369-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 07/05/2023] [Indexed: 07/28/2023] Open
Abstract
A wealth of pre-clinical reports and data derived from human subjects and brain autopsies suggest that microbial infections are relevant to Alzheimer's disease (AD). This has inspired the hypothesis that microbial infections increase the risk or even trigger the onset of AD. Multiple models have been developed to explain the increase in pathogenic microbes in AD patients. Although this hypothesis is well accepted in the field, it is not yet clear whether microbial neuroinvasion is a cause of AD or a consequence of the pathological changes experienced by the demented brain. Along the same line, the gut microbiome has also been proposed as a modulator of AD. In this review, we focus on human-based evidence demonstrating the elevated abundance of microbes and microbe-derived molecules in AD hosts as well as their interactions with AD hallmarks. Further, the direct-purpose and potential off-target effects underpinning the efficacy of anti-microbial treatments in AD are also addressed.
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Affiliation(s)
- Celso S G Catumbela
- Department of Neurology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Vijayasree V Giridharan
- Translational Psychiatry Program, Faillace Department of Psychiatry and Behavioral Sciences, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, 77054, USA
| | - Tatiana Barichello
- Translational Psychiatry Program, Faillace Department of Psychiatry and Behavioral Sciences, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, 77054, USA
- Graduate Program in Health Sciences, University of Southern Santa Catarina (UNESC), Criciúma, SC, 88806-000, Brazil
| | - Rodrigo Morales
- Department of Neurology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA.
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O'Higgins, 8370993, Santiago, Chile.
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Visentin D, Gobin I, Maglica Ž. Periodontal Pathogens and Their Links to Neuroinflammation and Neurodegeneration. Microorganisms 2023; 11:1832. [PMID: 37513004 PMCID: PMC10385044 DOI: 10.3390/microorganisms11071832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/05/2023] [Accepted: 07/14/2023] [Indexed: 07/30/2023] Open
Abstract
Pathogens that play a role in the development and progression of periodontitis have gained significant attention due to their implications in the onset of various systemic diseases. Periodontitis is characterized as an inflammatory disease of the gingival tissue that is mainly caused by bacterial pathogens. Among them, Porphyromonas gingivalis, Treponema denticola, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Tannerella forsythia are regarded as the main periodontal pathogens. These pathogens elicit the release of cytokines, which in combination with their virulence factors induce chronic systemic inflammation and subsequently impact neural function while also altering the permeability of the blood-brain barrier. The primary objective of this review is to summarize the existing information regarding periodontal pathogens, their virulence factors, and their potential association with neuroinflammation and neurodegenerative diseases. We systematically reviewed longitudinal studies that investigated the association between periodontal disease and the onset of neurodegenerative disorders. Out of the 24 studies examined, 20 showed some degree of positive correlation between periodontal disease and neurodegenerative disorders, with studies focusing on cognitive function demonstrating the most robust effects. Therefore, periodontal pathogens might represent an exciting new approach to develop novel preventive treatments for neurodegenerative diseases.
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Affiliation(s)
- David Visentin
- Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia
| | - Ivana Gobin
- Department of Microbiology and Parasitology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia
| | - Željka Maglica
- Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia
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14
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Grobler C, van Tongeren M, Gettemans J, Kell DB, Pretorius E. Alzheimer's Disease: A Systems View Provides a Unifying Explanation of Its Development. J Alzheimers Dis 2023; 91:43-70. [PMID: 36442193 DOI: 10.3233/jad-220720] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Alzheimer's disease (AD) is a debilitating neurodegenerative disorder affecting 50 million people globally. It is characterized by the presence of extracellular senile plaques and intracellular neurofibrillary tangles, consisting of amyloid-β and hyperphosphorylated tau proteins, respectively. Despite global research efforts, there is currently no cure available, due in part to an incomplete understanding of the disease pathogenesis. Numerous possible mechanisms, or hypotheses, explaining the origins of sporadic or late-onset AD have been proposed, including the amyloid-β, inflammatory, vascular, and infectious hypotheses. However, despite ample evidence, the failure of multiple trial drugs at the clinical stage illuminates the possible pitfalls of these hypotheses. Systems biology is a strategy which aims to elucidate the interactions between parts of a whole. Using this approach, the current paper shows how the four previously mentioned hypotheses of AD pathogenesis can be intricately connected. This approach allows for seemingly contradictory evidence to be unified in a system-focused explanation of sporadic AD development. Within this view, it is seen that infectious agents, such as P. gingivalis, may play a central role. The data presented here shows that when present, P. gingivalis or its virulence factors, such as gingipains, may induce or exacerbate pathologies underlying sporadic AD. This evidence supports the view that infectious agents, and specifically P. gingivalis, may be suitable treatment targets in AD.
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Affiliation(s)
- Corlia Grobler
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa
| | - Marvi van Tongeren
- Department of Biomolecular Medicine, Faculty of Medicine & Health Sciences, Ghent University, Ghent, Belgium
| | - Jan Gettemans
- Department of Biomolecular Medicine, Faculty of Medicine & Health Sciences, Ghent University, Ghent, Belgium
| | - Douglas B Kell
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa.,Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, UK.,The Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Etheresia Pretorius
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa.,Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, UK
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15
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Liu S, Dashper SG, Zhao R. Association Between Oral Bacteria and Alzheimer's Disease: A Systematic Review and Meta-Analysis. J Alzheimers Dis 2023; 91:129-150. [PMID: 36404545 DOI: 10.3233/jad-220627] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Pre-clinical evidence implicates oral bacteria in the pathogenesis of Alzheimer's disease (AD), while clinical studies show diverse results. OBJECTIVE To comprehensively assess the association between oral bacteria and AD with clinical evidence. METHODS Studies investigating the association between oral bacteria and AD were identified through a systematic search of six databases PubMed, Embase, Cochrane Central Library, Scopus, ScienceDirect, and Web of Science. Methodological quality ratings of the included studies were performed. A best evidence synthesis was employed to integrate the results. When applicable, a meta-analysis was conducted using a random-effect model. RESULTS Of the 16 studies included, ten investigated periodontal pathobionts and six were microbiome-wide association studies. Samples from the brain, serum, and oral cavity were tested. We found over a ten-fold and six-fold increased risk of AD when there were oral bacteria (OR = 10.68 95% CI: 4.48-25.43; p < 0.00001, I2 = 0%) and Porphyromonas gingivalis (OR = 6.84 95% CI: 2.70-17.31; p < 0.0001, I2 = 0%) respectively in the brain. While AD patients exhibited lower alpha diversity of oral microbiota than healthy controls, the findings of bacterial communities were inconsistent among studies. The best evidence synthesis suggested a moderate level of evidence for an overall association between oral bacteria and AD and for oral bacteria being a risk factor for AD. CONCLUSION Current evidence moderately supports the association between oral bacteria and AD, while the association was strong when oral bacteria were detectable in the brain. Further evidence is needed to clarify the interrelationship between both individual species and bacterial communities and the development of AD.
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Affiliation(s)
- Sixin Liu
- School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Stuart G Dashper
- Centre for Oral Health Research, Melbourne Dental School, Bio21 Institute, The University of Melbourne, Parkville, Australia
| | - Rui Zhao
- Department of Stomatology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China
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16
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Pisani F, Pisani V, Arcangeli F, Harding A, Singhrao SK. Locus Coeruleus Dysfunction and Trigeminal Mesencephalic Nucleus Degeneration: A Cue for Periodontal Infection Mediated Damage in Alzheimer's Disease? INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1007. [PMID: 36673763 PMCID: PMC9858796 DOI: 10.3390/ijerph20021007] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 12/30/2022] [Accepted: 01/01/2023] [Indexed: 06/12/2023]
Abstract
Alzheimer's disease (AD) is a leading neurodegenerative disease with deteriorating cognition as its main clinical sign. In addition to the clinical history, it is characterized by the presence of two neuropathological hallmark lesions; amyloid-beta (Aβ) and neurofibrillary tangles (NFTs), identified in the brain at post-mortem in specific anatomical areas. Recently, it was discovered that NFTs occur initially in the subcortical nuclei, such as the locus coeruleus in the pons, and are said to spread from there to the cerebral cortices and the hippocampus. This contrasts with the prior acceptance of their neuropathology in the enthorinal cortex and the hippocampus. The Braak staging system places the accumulation of phosphorylated tau (p-tau) binding to NFTs in the locus coeruleus and other subcortical nuclei to precede stages I-IV. The locus coeruleus plays diverse psychological and physiological roles within the human body including rapid eye movement sleep disorder, schizophrenia, anxiety, and depression, regulation of sleep-wake cycles, attention, memory, mood, and behavior, which correlates with AD clinical behavior. In addition, the locus coeruleus regulates cardiovascular, respiratory, and gastrointestinal activities, which have only recently been associated with AD by modern day research enabling the wider understanding of AD development via comorbidities and microbial dysbiosis. The focus of this narrative review is to explore the modes of neurodegeneration taking place in the locus coeruleus during the natural aging process of the trigeminal nerve connections from the teeth and microbial dysbiosis, and to postulate a pathogenetic mechanism due to periodontal damage and/or infection focused on Treponema denticola.
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Affiliation(s)
- Flavio Pisani
- Programme Lead, MSc/MClinDent in Clinical Periodontology, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston PR1 2HE, UK
| | - Valerio Pisani
- I.R.C.C.S. “Santa Lucia” Foundation, Neurology and Neurorehabilitation Unit, Via Ardeatina, 306, 00179 Rome, Italy
| | - Francesca Arcangeli
- Azienda Sanitaria Locale ASLRM1, Nuovo Regina Margherita Hospital, Geriatric Department-Advanced Centre for Dementia and Cognitive Disorders, Via Emilio Morosini, 30, 00153 Rome, Italy
| | - Alice Harding
- Dementia and Neurodegenerative Disease Research Group, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston PR1 2HE, UK
| | - Sim K. Singhrao
- Dementia and Neurodegenerative Disease Research Group, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston PR1 2HE, UK
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17
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Salhi L, Al Taep Y, Salmon E, Van Hede D, Lambert F. How Periodontitis or Periodontal Bacteria Can Influence Alzheimer's Disease Features? A Systematic Review of Pre-Clinical Studies. J Alzheimers Dis 2023; 96:979-1010. [PMID: 37927257 PMCID: PMC10741373 DOI: 10.3233/jad-230478] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2023] [Indexed: 11/07/2023]
Abstract
BACKGROUND The negative effects of periodontitis on systemic diseases, including diabetes, cardiovascular diseases, and Alzheimer's disease (AD), have been widely described. OBJECTIVE This systematic review aimed to gather the current understanding of the pathophysiological mechanisms linking periodontitis to AD. METHODS An electronic systematic search of the PubMed/MEDLINE, Scopus, and Embase databases was performed using the following PECO question: How can periodontitis or periodontal bacteria influence Alzheimer's disease features?". Only preclinical studies exploring the biological links between periodontitis and AD pathology were included. This study was registered at the International Prospective Register of Systematic Reviews (PROSPERO), and the Syrcle and Camarades protocols were used to assess the risk of bias. RESULTS After a systematic screening of titles and abstracts (n = 3,307), thirty-six titles were selected for abstract reading, of which 13 were excluded (k = 1), resulting in the inclusion of 23 articles. Oral or systemic exposure to periodontopathogens or their byproducts is responsible for both in situ brain manifestations and systemic effects. Significant elevated rates of cytokines and amyloid peptides (Aβ) and derivate products were found in both serum and brain. Additionally, in infected animals, hyperphosphorylation of tau protein, hippocampal microgliosis, and neuronal death were observed. Exposure to periodontal infection negatively impairs cognitive behavior, leading to memory decline. CONCLUSIONS Systemic inflammation and brain metastatic infections induced by periodontal pathogens contribute to neuroinflammation, amyloidosis, and tau phosphorylation, leading to brain damage and subsequent cognitive impairment.
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Affiliation(s)
- Leila Salhi
- Department of Periodontology, Oro-Dental and Implant Surgery, University Hospital of Liège, Liège, Belgium
| | - Yaman Al Taep
- Department of Periodontology, Oro-Dental and Implant Surgery, University Hospital of Liège, Liège, Belgium
| | - Eric Salmon
- Department of Neurology - Memory Clinic, University Hospital of Liège, Liège, Belgium
- GIGA Cyclotron Research Center, University of Liege, Liege, Belgium
| | - Dorien Van Hede
- Department of Periodontology, Oro-Dental and Implant Surgery, University Hospital of Liège, Liège, Belgium
| | - France Lambert
- Department of Periodontology, Oro-Dental and Implant Surgery, University Hospital of Liège, Liège, Belgium
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18
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Paudel D, Uehara O, Giri S, Yoshida K, Morikawa T, Kitagawa T, Matsuoka H, Miura H, Toyofuku A, Kuramitsu Y, Ohta T, Kobayashi M, Abiko Y. Effect of psychological stress on the oral-gut microbiota and the potential oral-gut-brain axis. JAPANESE DENTAL SCIENCE REVIEW 2022; 58:365-375. [DOI: 10.1016/j.jdsr.2022.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 10/21/2022] [Accepted: 11/08/2022] [Indexed: 11/18/2022] Open
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19
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Nemergut M, Batkova T, Vigasova D, Bartos M, Hlozankova M, Schenkmayerova A, Liskova B, Sheardova K, Vyhnalek M, Hort J, Laczó J, Kovacova I, Sitina M, Matej R, Jancalek R, Marek M, Damborsky J. Increased occurrence of Treponema spp. and double-species infections in patients with Alzheimer's disease. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 844:157114. [PMID: 35787909 DOI: 10.1016/j.scitotenv.2022.157114] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 06/25/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
Although the link between microbial infections and Alzheimer's disease (AD) has been demonstrated in multiple studies, the involvement of pathogens in the development of AD remains unclear. Here, we investigated the frequency of the 10 most commonly cited viral (HSV-1, EBV, HHV-6, HHV-7, and CMV) and bacterial (Chlamydia pneumoniae, Helicobacter pylori, Borrelia burgdorferi, Porphyromonas gingivalis, and Treponema spp.) pathogens in serum, cerebrospinal fluid (CSF) and brain tissues of AD patients. We have used an in-house multiplex PCR kit for simultaneous detection of five bacterial and five viral pathogens in serum and CSF samples from 50 AD patients and 53 healthy controls (CTRL). We observed a significantly higher frequency rate of AD patients who tested positive for Treponema spp. compared to controls (AD: 62.2 %; CTRL: 30.3 %; p-value = 0.007). Furthermore, we confirmed a significantly higher occurrence of cases with two or more simultaneous infections in AD patients compared to controls (AD: 24 %; CTRL 7.5 %; p-value = 0.029). The studied pathogens were detected with comparable frequency in serum and CSF. In contrast, Borrelia burgdorferi, human herpesvirus 7, and human cytomegalovirus were not detected in any of the studied samples. This study provides further evidence of the association between microbial infections and AD and shows that paralleled analysis of multiple sample specimens provides complementary information and is advisable for future studies.
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Affiliation(s)
- Michal Nemergut
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic
| | - Tereza Batkova
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Department of Neurology, Masaryk University, St. Anne's University Hospital Brno, Brno, Czech Republic; BioVendor R&D, Brno, Czech Republic
| | - Dana Vigasova
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic
| | | | | | - Andrea Schenkmayerova
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic
| | - Barbora Liskova
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic
| | - Katerina Sheardova
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Department of Neurology, Masaryk University, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Martin Vyhnalek
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Department of Neurology, Charles University, Second Faculty of Medicine and Motol University Hospital, Prague, Czech Republic
| | - Jakub Hort
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Department of Neurology, Charles University, Second Faculty of Medicine and Motol University Hospital, Prague, Czech Republic
| | - Jan Laczó
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Department of Neurology, Charles University, Second Faculty of Medicine and Motol University Hospital, Prague, Czech Republic
| | - Ingrid Kovacova
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Michal Sitina
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Radoslav Matej
- Department of Pathology and Molecular Medicine, Third Faculty of Medicine, Charles University and Thomayer University Hospital, Prague, Czech Republic
| | - Radim Jancalek
- Department of Neurosurgery, St. Anne's University Hospital Brno, Brno, Czech Republic and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Martin Marek
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic
| | - Jiri Damborsky
- International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic; Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic.
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Treponema denticola Induces Neuronal Apoptosis by Promoting Amyloid-β Accumulation in Mice. Pathogens 2022; 11:pathogens11101150. [PMID: 36297207 PMCID: PMC9610539 DOI: 10.3390/pathogens11101150] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 09/29/2022] [Accepted: 10/02/2022] [Indexed: 11/13/2022] Open
Abstract
Background: Neuronal apoptosis is a major contributor to Alzheimer's disease (AD). Periodontitis is a significant risk factor for AD. The periodontal pathogens Porphyromonas gingivalis and Treponema denticola have been shown to initiate the hallmark pathologies and behavioral symptoms of AD. Studies have found that T. denticola infection induced Tau hyperphosphorylation and amyloid β accumulation in the hippocampi of mice. Aβ accumulation is closely associated with neuronal apoptosis. However, the roles of T. denticola in neuronal apoptosis remain unclear and its roles in AD pathology need further study. Objective: This study aimed to investigate whether oral infection with T. denticola induced alveolar bone loss and neuronal apoptosis in mice. Methods: C57BL/6 mice were orally administered with T. denticola, Micro-CT was employed to assess the alveolar bone resorption. Western blotting, quantitative PCR, and TUNEL staining were utilized to detect the apoptosis-associated changes in mouse hippocampi. N2a were co-cultured with T. denticola to verify in vivo results. Results: Mice infected with T. denticola exhibited more alveolar bone loss compared with the control mice. T. denticola oral infection induced neuronal apoptosis in hippocampi of mice. Consistent results of the apoptosis-associated protein expression were observed in N2a cells treated with T. denticola and Aβ1-42 in vitro. However, the Aβ inhibitor reversed these results, suggesting that Aβ1-42 mediates T. denticola infection-induced neuronal apoptosis. Conclusions: This study found that oral infected T. denticola caused alveolar bone loss, and induced neuronal apoptosis by promoting Aβ accumulation in mice, providing evidence for the link between periodontitis and AD.
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Gong T, Chen Q, Mao H, Zhang Y, Ren H, Xu M, Chen H, Yang D. Outer membrane vesicles of Porphyromonas gingivalis trigger NLRP3 inflammasome and induce neuroinflammation, tau phosphorylation, and memory dysfunction in mice. Front Cell Infect Microbiol 2022; 12:925435. [PMID: 36017373 PMCID: PMC9397999 DOI: 10.3389/fcimb.2022.925435] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 07/01/2022] [Indexed: 11/13/2022] Open
Abstract
BackgroundPorphyromonas gingivalis (Pg), the keystone pathogen in chronic periodontitis, is reported to initiate Alzheimer’s disease pathologies in preclinical studies. However, the specific mechanisms and signaling pathways acting on the brain still need to be further explored. Outer membrane vesicles are derived from Gram-negative bacteria and contain many virulence factors of bacteria. We hypothesized that outer membrane vesicles are an important weapon of Porphyromonas gingivalis to initiate Alzheimer’s disease pathologies.MethodsThe outer membrane vesicles of Porphyromonas gingivalis (Pg OMVs, 4 mg/kg) or saline were delivered to 14-month-old mice by oral gavage every other day for eight weeks. Behavioral alterations were assessed by the open field test, Morris water maze, and Y-maze test. Blood–brain barrier permeability, neuroinflammation, tau phosphorylation, and NLRP3 inflammasome-related protein were analyzed.ResultsPg OMVs impaired memory and learning ability of mice and decreased tight junction–related gene expression ZO-1, occludin, claudin-5, and occludin protein expression in the hippocampus. Pg OMVs could be detected in the hippocampus and cortex three days after oral gavage. Furthermore, Pg OMVs activated both astrocytes and microglia and elevated IL-1β, tau phosphorylation on the Thr231 site, and NLRP3 inflammasome–related protein expression in the hippocampus. In in vitro studies, Pg OMV (5 µg/ml) stimulation increased the mRNA and immunofluorescence of NLRP3 in BV2 microglia, which were significantly inhibited by the NLRP3 inhibitor MCC950. In contrast, the tau phosphorylation in N2a neurons was enhanced after treatment with conditioned media from Pg OMV-stimulated microglia, which was attenuated after pretreatment with MCC950.ConclusionsThese results indicate that Pg OMVs prompt memory dysfunction, neuroinflammation, and tau phosphorylation and trigger NLRP3 inflammasome in the brain of middle-aged mice. We propose that Pg OMVs play an important role in activating neuroinflammation in the AD-like pathology triggered by Porphyromonas gingivalis, and NLRP3 inflammasome activation is a possible mechanism.
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Affiliation(s)
- Ting Gong
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Qi Chen
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Hongchen Mao
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Yao Zhang
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Huan Ren
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Mengmeng Xu
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Hong Chen
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
| | - Deqin Yang
- Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing Medical University, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing Medical University, Chongqing, China
- *Correspondence: Deqin Yang,
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22
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The Mechanistic Pathways of Periodontal Pathogens Entering the Brain: The Potential Role of Treponema denticola in Tracing Alzheimer’s Disease Pathology. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19159386. [PMID: 35954742 PMCID: PMC9368682 DOI: 10.3390/ijerph19159386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 11/20/2022]
Abstract
Alzheimer’s Disease (AD) is a complex neurodegenerative disease and remains the most common form of dementia. The pathological features include amyloid (Aβ) accumulation, neurofibrillary tangles (NFTs), neural and synaptic loss, microglial cell activation, and an increased blood–brain barrier permeability. One longstanding hypothesis suggests that a microbial etiology is key to AD initiation. Among the various periodontal microorganisms, Porphyromonas gingivalis has been considered the keystone agent to potentially correlate with AD, due to its influence on systemic inflammation. P. gingivalis together with Treponema denticola and Tannerella forsythia belong to the red complex consortium of bacteria advocated to sustain periodontitis within a local dysbiosis and a host response alteration. Since the implication of P. gingivalis in the pathogenesis of AD, evidence has emerged of T. denticola clusters in some AD brain tissue sections. This narrative review explored the potential mode of spirochetes entry into the AD brain for tracing pathology. Spirochetes are slow-growing bacteria, which can hide within ganglia for many years. It is this feature in combination with the ability of these bacteria to evade the hosts’ immune responses that may account for a long lag phase between infection and plausible AD disease symptoms. As the locus coeruleus has direct connection between the trigeminal nuclei to periodontal free nerve endings and proprioceptors with the central nervous system, it is plausible that they could initiate AD pathology from this anatomical region.
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Seymour T, Zhang J. Porphyromonas Gingivalis in the Pathogenesis of Alzheimer’s Disease and Its Therapeutic Target. JOURNAL OF EXPLORATORY RESEARCH IN PHARMACOLOGY 2022; 7:45-53. [DOI: 10.14218/jerp.2021.00030] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Jungbauer G, Stähli A, Zhu X, Auber Alberi L, Sculean A, Eick S. Periodontal microorganisms and Alzheimer disease - A causative relationship? Periodontol 2000 2022; 89:59-82. [PMID: 35244967 PMCID: PMC9314828 DOI: 10.1111/prd.12429] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 12/07/2021] [Accepted: 12/21/2021] [Indexed: 01/10/2023]
Abstract
In the initiation or exacerbation of Alzheimer disease, the dissemination of oral microorganisms into the brain tissue or the low‐level systemic inflammation have been speculated to play a role. However, the impact of oral microorganisms, such as Porphyromonas gingivalis, on the pathogenesis of Alzheimer disease and the potential causative relationship is still unclear. The present review has critically reviewed the literature by examining the following aspects: (a) the oral microbiome and the immune response in the elderly population, (b) human studies on the association between periodontal and gut microorganisms and Alzheimer disease, (c) animal and in vitro studies on microorganisms and Alzheimer disease, and (d) preventive and therapeutic approaches. Factors contributing to microbial dysbiosis seem to be aging, local inflammation, systemic diseases, wearing of dentures, living in nursing homes and no access to adequate oral hygiene measures. Porphyromonas gingivalis was detectable in post‐mortem brain samples. Microbiome analyses of saliva samples or oral biofilms showed a decreased microbial diversity and a different composition in Alzheimer disease compared to cognitively healthy subjects. Many in‐vitro and animal studies underline the potential of P gingivalis to induce Alzheimer disease‐related alterations. In animal models, recurring applications of P gingivalis or its components increased pro‐inflammatory mediators and β‐amyloid in the brain and deteriorated the animals' cognitive performance. Since periodontitis is the result of a disturbed microbial homoeostasis, an effect of periodontal therapy on the oral microbiome and host response related to cognitive parameters may be suggested and should be elucidated in further clinical trials.
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Affiliation(s)
- Gert Jungbauer
- Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.,Private Dental Practice, Straubing, Germany
| | - Alexandra Stähli
- Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | - Xilei Zhu
- Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | | | - Anton Sculean
- Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | - Sigrun Eick
- Department of Periodontology, School of Dental Medicine, University of Bern, Bern, Switzerland
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Tang Z, Cheng X, Su X, Wu L, Cai Q, Wu H. Treponema denticola Induces Alzheimer-Like Tau Hyperphosphorylation by Activating Hippocampal Neuroinflammation in Mice. J Dent Res 2022; 101:992-1001. [PMID: 35193423 DOI: 10.1177/00220345221076772] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Alzheimer's disease (AD) is the most common type of dementia. Tau hyperphosphorylation and amyloid β (Aβ) deposition are the key pathological hallmarks of AD. Recent studies have shown that periodontitis is a significant risk factor for AD. The periodontal pathogen Porphyromonas gingivalis and its virulence factors have been shown to initiate and promote the hallmark pathologies and behavioral symptoms of AD. A possible link between Treponema denticola, another main periodontal pathogen, and AD has been reported. However, the role of T. denticola in AD pathogenesis is still unclear, and whether T. denticola and P. gingivalis exert a synergistic effect to promote AD development needs to be further studied. In this study, we investigated whether oral infection with T. denticola caused tau hyperphosphorylation in the hippocampi of mice and explored the underlying mechanisms. Orally administered T. denticola induced alveolar bone resorption, colonized brain tissues, and increased the activity of the phosphokinase GSK3β by activating neuroinflammation in the hippocampus, thus promoting the hyperphosphorylation of the tau protein at Ser396, Thr181, and Thr231 in mice. An in vitro study with BV2 and N2a cell models of T. denticola invasion also verified the role of this pathogen in tau phosphorylation. T. denticola and P. gingivalis were not found to exert a synergistic effect on tau phosphorylation. In summary, these findings provide new insight into the important role of T. denticola in AD pathogenesis, providing biological connections between periodontal diseases and AD.
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Affiliation(s)
- Z Tang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - X Cheng
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - X Su
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - L Wu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Q Cai
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - H Wu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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Tadjoedin FM, Masulili SLC, Rizal MI, Kusdhany LS, Turana Y, Ismail RI, Bachtiar BM. The Red and Orange Complex Subgingival Microbiome of Cognitive Impairment and Cognitively Normal Elderly with Periodontitis. Geriatrics (Basel) 2022; 7:geriatrics7010012. [PMID: 35076522 PMCID: PMC8788293 DOI: 10.3390/geriatrics7010012] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/28/2021] [Accepted: 12/31/2021] [Indexed: 12/03/2022] Open
Abstract
Increasing evidence has shown an association between periodontitis and cognitive impairment. Subgingival microbiota play a great role in periodontitis pathogenesis. However, the correlation between the subgingival microbiome and cognitive impairment remains unclear. This study aimed to evaluate the red and orange complex subgingival microbiome of cognitively impaired and cognitively normal elderly Indonesian subjects with periodontitis. Twenty-eight elderly subjects diagnosed with periodontitis underwent two cognitive examinations using the Hopkins Verbal Learning Test and the Mini-Mental State Examination. Gingival crevicular fluid taken from the periodontal pocket, at a depth between 5 and 7 mm, using a paper point was used as the subgingival samples. The subgingival microbiome in the cognitive impairment group (n = 14) and cognitively normal group (n = 14) was compared using the 16S rRNA Metagenomic iSeq™ 100 Sequencing System. There was β-diversity in the subgingival microbiota between the cognitively impaired and cognitively normal subjects. The metagenomic analysis showed a higher abundance of Porphyromonas and Treponema bacteria in the cognitive impairment group than in the normal cognitive group (p < 0.05). The abundance of Porphyromonas gingivalis and Treponema denticola was higher in the cognitively impaired elderly subjects. The role of P. gingivalis and T. denticola in the pathogenesis of cognitive impairment needs further investigation.
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Affiliation(s)
- Fatimah Maria Tadjoedin
- Doctoral Program, Faculty of Dentistry, Universitas Indonesia, Jakarta 10430, Indonesia; (F.M.T.); (M.I.R.)
- Department of Periodontics, Faculty of Dentistry, Universitas Indonesia, Jakarta 10430, Indonesia
| | - Sri Lelyati C. Masulili
- Department of Periodontics, Faculty of Dentistry, Universitas Indonesia, Jakarta 10430, Indonesia
- Correspondence:
| | - Muhammad Ihsan Rizal
- Doctoral Program, Faculty of Dentistry, Universitas Indonesia, Jakarta 10430, Indonesia; (F.M.T.); (M.I.R.)
- Department of Oral Biology, Faculty of Dentistry, Trisakti University, Jakarta 11440, Indonesia
| | - Lindawati S. Kusdhany
- Department of Prosthodontics, Faculty of Dentistry, Universitas Indonesia, Jakarta 10430, Indonesia;
| | - Yuda Turana
- Department of Neurology, School of Medicine and Health Sciences, Atma Jaya Catholic University of Indonesia, Jakarta 14440, Indonesia;
| | - Raden Irawati Ismail
- Department of Psychiatry, Faculty of Medicine Universitas Indonesia—Cipto Mangunkusumo General Hospital, Jakarta 10430, Indonesia;
| | - Boy M. Bachtiar
- Department of Oral Biology, Faculty of Dentistry, Universitas Indonesia, Jakarta 10430, Indonesia;
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Kouki MA, Pritchard AB, Alder JE, Crean S. Do Periodontal Pathogens or Associated Virulence Factors Have a Deleterious Effect on the Blood-Brain Barrier, Contributing to Alzheimer's Disease? J Alzheimers Dis 2021; 85:957-973. [PMID: 34897087 DOI: 10.3233/jad-215103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The central nervous system (CNS) is protected by a highly selective barrier, the blood-brain barrier (BBB), that regulates the exchange and homeostasis of bloodborne molecules, excluding xenobiotics. This barrier forms the first line of defense by prohibiting pathogens from crossing to the CNS. Aging and chronic exposure of the BBB to pathogens renders it permeable, and this may give rise to pathology in the CNS such as Alzheimer's disease (AD). Researchers have linked pathogens associated with periodontitis to neuroinflammation and AD-like pathology in vivo and in vitro. Although the presence of periodontitis-associated bacteria has been linked to AD in several clinical studies as DNA and virulence factors were confirmed in brain samples of human AD subjects, the mechanism by which the bacteria traverse to the brain and potentially influences neuropathology is unknown. In this review, we present current knowledge about the association between periodontitis and AD, the mechanism whereby periodontal pathogens might provoke neuroinflammation and how periodontal pathogens could affect the BBB. We suggest future studies, with emphasis on the use of human in vitro models of cells associated with the BBB to unravel the pathway of entry for these bacteria to the CNS and to reveal the molecular and cellular pathways involved in initiating the AD-like pathology. In conclusion, evidence demonstrate that bacteria associated with periodontitis and their virulence factors are capable of inflecting damage to the BBB and have a role in giving rise to pathology similar to that found in AD.
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Affiliation(s)
- Mhd Ammar Kouki
- Brain and Behaviour Centre, Faculty of Clinical and Biomedical Sciences, School of Pharmacy and Biomedical Sciences, University of Central Lancashire, Preston, UK
| | - Anna Barlach Pritchard
- Brain and Behaviour Centre, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston, UK
| | - Jane Elizabeth Alder
- Brain and Behaviour Centre, Faculty of Clinical and Biomedical Sciences, School of Pharmacy and Biomedical Sciences, University of Central Lancashire, Preston, UK
| | - StJohn Crean
- Brain and Behaviour Centre, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston, UK
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Rice AO. Alzheimer's Disease and Oral-Systemic Health: Bidirectional Care Integration Improving Outcomes. FRONTIERS IN ORAL HEALTH 2021; 2:674329. [PMID: 35048018 PMCID: PMC8757752 DOI: 10.3389/froh.2021.674329] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/28/2021] [Indexed: 12/15/2022] Open
Abstract
Dentistry is an effective healthcare field that can impact Alzheimer's disease through prevention and education. Every day dental providers use an arsenal of assessment protocols directly coinciding with modifiable Alzheimer's risk factors. An innovative way to help in the prevention of Alzheimer's disease is to utilize oral health professionals who reach the public in ways other health care providers may not. Bidirectional care integration is needed to stifle many systemic diseases and Alzheimer's disease is no different. Ultimately with collaborative care the patient reaps the benefits. Alzheimer's is associated with many etiologies and pathophysiological processes. These include cardiovascular health, smoking, sleep, inflammatory pathogens, and diabetes. In the United States, dental providers assess each of these factors daily and can be instrumental in educating patients on the influence of these factors for dementia prevention. Globally, by 2025, the number of people with Alzheimer's disease is expected to rise by at least 14%. Such increases will strain local and national health care systems, but for the US if Medicare were expanded to include dental services, many older adults could be spared needless suffering. The goal of this perspective article is to highlight existing practices being used in the field of dentistry that can easily be adapted to educate patients in preventive care and treat risk factors. It is the duty of healthcare professionals to explore all opportunities to stem the advance of this disease and by integrating oral and systemic health into transdisciplinary science, health care and policy may do just that.
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Affiliation(s)
- Anne O. Rice
- Oral Systemic Seminars, Conroe, TX, United States
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