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Chang SC, Arifin MI, Tahir W, McDonald KJ, Zeng D, Schatzl HM, Hannaoui S, Gilch S. Extraneural infection route restricts prion conformational variability and attenuates the impact of quaternary structure on infectivity. PLoS Pathog 2024; 20:e1012370. [PMID: 38976748 PMCID: PMC11257401 DOI: 10.1371/journal.ppat.1012370] [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: 03/26/2024] [Revised: 07/18/2024] [Accepted: 06/25/2024] [Indexed: 07/10/2024] Open
Abstract
Prions can exist as different strains that consist of conformational variants of the misfolded, pathogenic prion protein isoform PrPSc. Defined by stably transmissible biological and biochemical properties, strains have been identified in a spectrum of prion diseases, including chronic wasting disease (CWD) of wild and farmed cervids. CWD is highly contagious and spreads via direct and indirect transmission involving extraneural sites of infection, peripheral replication and neuroinvasion of prions. Here, we investigated the impact of infection route on CWD prion conformational selection and propagation. We used gene-targeted mouse models expressing deer PrP for intracerebral or intraperitoneal inoculation with fractionated or unfractionated brain homogenates from white-tailed deer, harboring CWD strains Wisc-1 or 116AG. Upon intracerebral inoculation, Wisc-1 and 116AG-inoculated mice differed in conformational stability of PrPSc. In brains of mice infected intraperitoneally with either inoculum, PrPSc propagated with identical conformational stability and fewer PrPSc deposits in most brain regions than intracerebrally inoculated animals. For either inoculum, PrPSc conformational stability in brain and spinal cord was similar upon intracerebral infection but significantly higher in spinal cords of intraperitoneally infected animals. Inoculation with fractionated brain homogenates resulted in lower variance of survival times upon intraperitoneal compared to intracerebral infection. In summary, we demonstrate that extraneural infection mitigates the impact of PrPSc quaternary structure on infection and reduces conformational variability of PrPSc propagated in the brain. These findings provide new insights into the evolution of stable CWD strains in natural, extraneural transmissions.
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Affiliation(s)
- Sheng Chun Chang
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | | | - Waqas Tahir
- Canadian and WOAH Reference Laboratory for BSE, Canadian Food Inspection Agency, Lethbridge, Canada
| | | | - Doris Zeng
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Hermann M. Schatzl
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Canada
| | - Samia Hannaoui
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Sabine Gilch
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
- Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Canada
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2
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Bali V, Grubišić V. Enteric glia as friends and foes of the intestinal epithelial barrier function. Front Immunol 2024; 15:1394654. [PMID: 38873614 PMCID: PMC11169670 DOI: 10.3389/fimmu.2024.1394654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 05/07/2024] [Indexed: 06/15/2024] Open
Affiliation(s)
- Vedrana Bali
- Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, United States
| | - Vladimir Grubišić
- Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, United States
- Center for Biomedical Innovation, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, United States
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3
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Kobashigawa E, Russell S, Zhang MZ, Sinnott EA, Connolly M, Zhang S. RT-QuIC detection of chronic wasting disease prion in platelet samples of white-tailed deer. BMC Vet Res 2024; 20:152. [PMID: 38654224 DOI: 10.1186/s12917-024-04005-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 04/04/2024] [Indexed: 04/25/2024] Open
Abstract
BACKGROUND Chronic wasting disease (CWD) is a prion disease of captive and free-ranging cervids. Currently, a definitive diagnosis of CWD relies on immunohistochemistry detection of PrPSc in the obex and retropharyngeal lymph node (RPLN) of the affected cervids. For high-throughput screening of CWD in wild cervids, RPLN samples are tested by ELISA followed by IHC confirmation of positive results. Recently, real-time quacking-induced conversion (RT-QuIC) has been used to detect CWD positivity in various types of samples. To develop a blood RT-QuIC assay suitable for CWD diagnosis, this study evaluated the assay sensitivity and specificity with and without ASR1-based preanalytical enrichment and NaI as the main ionic component in assay buffer. RESULTS A total of 23 platelet samples derived from CWD-positive deer (ELISA + /IHC +) and 30 platelet samples from CWD-negative (ELISA-) deer were tested. The diagnostic sensitivity was 43.48% (NaCl), 65.22% (NaI), 60.87% (NaCl-ASR1) or 82.61% (NaI-ASR1). The diagnostic specificity was 96.67% (NaCl), 100% (NaI), 100% (NaCl-ASR1), or 96.67% (NaI-ASR1). The probability of detecting CWD prion in platelet samples derived from CWD-positive deer was 0.924 (95% CRI: 0.714, 0.989) under NaI-ASR1 experimental condition and 0.530 (95% CRI: 0.156, 0.890) under NaCl alone condition. The rate of amyloid formation (RFA) was greatest under the NaI-ASR1 condition at 10-2 (0.01491, 95% CRI: 0.00675, 0.03384) and 10-3 (0.00629, 95% CRI: 0.00283, 0.01410) sample dilution levels. CONCLUSIONS Incorporation of ASR1-based preanalytical enrichment and NaI as the main ionic component significantly improved the sensitivity of CWD RT-QuIC on deer platelet samples. Blood test by the improved RT-QuIC assay may be used for antemortem and postmortem diagnosis of CWD.
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Affiliation(s)
- Estela Kobashigawa
- Veterinary Medical Diagnostic Laboratory, College of Veterinary Medicine, University of Missouri, 901 E. Campus Loop, Columbia, MO, USA
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, 901 E. Campus Loop, Columbia, MO, USA
| | - Sherri Russell
- Missouri Department of Conservation, 2901 W Truman Blvd, Jefferson City, MO, USA
| | - Michael Z Zhang
- Veterinary Medical Diagnostic Laboratory, College of Veterinary Medicine, University of Missouri, 901 E. Campus Loop, Columbia, MO, USA
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, 901 E. Campus Loop, Columbia, MO, USA
| | - Emily A Sinnott
- Missouri Department of Conservation, 2901 W Truman Blvd, Jefferson City, MO, USA
| | - Michael Connolly
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 67 Cyclotron Rd, Berkeley, CA, USA
| | - Shuping Zhang
- Veterinary Medical Diagnostic Laboratory, College of Veterinary Medicine, University of Missouri, 901 E. Campus Loop, Columbia, MO, USA.
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, 901 E. Campus Loop, Columbia, MO, USA.
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Mao X, Shen J. Potential roles of enteric glial cells in Crohn's disease: A critical review. Cell Prolif 2024; 57:e13536. [PMID: 37551711 PMCID: PMC10771111 DOI: 10.1111/cpr.13536] [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: 01/31/2023] [Revised: 07/23/2023] [Accepted: 07/26/2023] [Indexed: 08/09/2023] Open
Abstract
Enteric glial cells in the enteric nervous system are critical for the regulation of gastrointestinal homeostasis. Increasing evidence suggests two-way communication between enteric glial cells and both enteric neurons and immune cells. These interactions may be important in the pathogenesis of Crohn's disease (CD), a chronic relapsing disease characterized by a dysregulated immune response. Structural abnormalities in glial cells have been identified in CD. Furthermore, classical inflammatory pathways associated with CD (e.g., the nuclear factor kappa-B pathway) function in enteric glial cells. However, the specific mechanisms by which enteric glial cells contribute to CD have not been summarized in detail. In this review, we describe the possible roles of enteric glial cells in the pathogenesis of CD, including the roles of glia-immune interactions, neuronal modulation, neural plasticity, and barrier integrity. Additionally, the implications for the development of therapeutic strategies for CD based on enteric glial cell-mediated pathogenic processes are discussed.
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Affiliation(s)
- Xinyi Mao
- Division of Gastroenterology and HepatologyBaoshan Branch, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghaiChina
- Division of Gastroenterology and Hepatology, Key Laboratory of Gastroenterology and HepatologyMinistry of Health, Inflammatory Bowel Disease Research Center, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive DiseaseShanghaiChina
| | - Jun Shen
- Division of Gastroenterology and HepatologyBaoshan Branch, Renji Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghaiChina
- Division of Gastroenterology and Hepatology, Key Laboratory of Gastroenterology and HepatologyMinistry of Health, Inflammatory Bowel Disease Research Center, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive DiseaseShanghaiChina
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5
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Sun JL, Telling GC. New developments in prion disease research using genetically modified mouse models. Cell Tissue Res 2023; 392:33-46. [PMID: 36929219 DOI: 10.1007/s00441-023-03761-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 03/03/2023] [Indexed: 03/18/2023]
Abstract
While much of what we know about the general principles of protein-based information transfer derives from studies of experimentally adapted rodent prions, these laboratory strains are limited in their ability to recapitulate features of human and animal prions and the diseases they produce. Here, we review how recent approaches using genetically modified mice have informed our understanding of naturally occurring prion diseases, their strain properties, and the factors controlling their transmission and evolution. In light of the increasing importance of chronic wasting disease, the application of mouse transgenesis to study this burgeoning and highly contagious prion disorder, in particular recent insights derived from gene-targeting approaches, will be a major focus of this review.
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Affiliation(s)
- Julianna L Sun
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, USA
| | - Glenn C Telling
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, USA.
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Seguella L, Gulbransen BD. Enteric glial biology, intercellular signalling and roles in gastrointestinal disease. Nat Rev Gastroenterol Hepatol 2021; 18:571-587. [PMID: 33731961 PMCID: PMC8324524 DOI: 10.1038/s41575-021-00423-7] [Citation(s) in RCA: 130] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/28/2021] [Indexed: 02/07/2023]
Abstract
One of the most transformative developments in neurogastroenterology is the realization that many functions normally attributed to enteric neurons involve interactions with enteric glial cells: a large population of peripheral neuroglia associated with enteric neurons throughout the gastrointestinal tract. The notion that glial cells function solely as passive support cells has been refuted by compelling evidence that demonstrates that enteric glia are important homeostatic cells of the intestine. Active signalling mechanisms between enteric glia and neurons modulate gastrointestinal reflexes and, in certain circumstances, function to drive neuroinflammatory processes that lead to long-term dysfunction. Bidirectional communication between enteric glia and immune cells contributes to gastrointestinal immune homeostasis, and crosstalk between enteric glia and cancer stem cells regulates tumorigenesis. These neuromodulatory and immunomodulatory roles place enteric glia in a unique position to regulate diverse gastrointestinal disease processes. In this Review, we discuss current concepts regarding enteric glial development, heterogeneity and functional roles in gastrointestinal pathophysiology and pathophysiology, with a focus on interactions with neurons and immune cells. We also present a working model to differentiate glial states based on normal function and disease-induced dysfunctions.
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Affiliation(s)
- Luisa Seguella
- Department of Physiology and Pharmacology "V. Erspamer", Sapienza University of Rome, Rome, Italy
- Department of Physiology, Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Brian D Gulbransen
- Department of Physiology, Neuroscience Program, Michigan State University, East Lansing, MI, USA.
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7
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Escobar LE, Pritzkow S, Winter SN, Grear DA, Kirchgessner MS, Dominguez-Villegas E, Machado G, Peterson AT, Soto C. The ecology of chronic wasting disease in wildlife. Biol Rev Camb Philos Soc 2020; 95:393-408. [PMID: 31750623 PMCID: PMC7085120 DOI: 10.1111/brv.12568] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 10/11/2019] [Accepted: 10/16/2019] [Indexed: 12/13/2022]
Abstract
Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection for other domestic and wildlife species is also plausible. Here, we review the current status of the knowledge with respect to CWD ecology in wildlife. Our current understanding of the geographic distribution of CWD lacks spatial and temporal detail, does not consider the biogeography of infectious diseases, and is largely biased by sampling based on hunters' cooperation and funding available for each region. Limitations of the methods used for data collection suggest that the extent and prevalence of CWD in wildlife is underestimated. If the zoonotic potential of CWD is confirmed in the short term, as suggested by recent results obtained in experimental animal models, there will be limited accurate epidemiological data to inform public health. Research gaps in CWD prion ecology include the need to identify specific biological characteristics of potential CWD reservoir species that better explain susceptibility to spillover, landscape and climate configurations that are suitable for CWD transmission, and the magnitude of sampling bias in our current understanding of CWD distribution and risk. Addressing these research gaps will help anticipate novel areas and species where CWD spillover is expected, which will inform control strategies. From an ecological perspective, control strategies could include assessing restoration of natural predators of CWD reservoirs, ultrasensitive CWD detection in biotic and abiotic reservoirs, and deer density and landscape modification to reduce CWD spread and prevalence.
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Affiliation(s)
- Luis E. Escobar
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, 24061, U.S.A
| | - Sandra Pritzkow
- Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, Houston, TX, 77030, U.S.A
| | - Steven N. Winter
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, 24061, U.S.A
| | - Daniel A. Grear
- US Geological Survey National Wildlife Health Center, Madison, WI, 59711, U.S.A
| | | | | | - Gustavo Machado
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, 27606, U.S.A
| | - A. Townsend Peterson
- Biodiversity Institute and Department of Ecology and Evolutionary Biology, The University of Kansas, Lawrence, KS, 66045, U.S.A
| | - Claudio Soto
- Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, Houston, TX, 77030, U.S.A
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8
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Seguella L, Capuano R, Sarnelli G, Esposito G. Play in advance against neurodegeneration: exploring enteric glial cells in gut-brain axis during neurodegenerative diseases. Expert Rev Clin Pharmacol 2019; 12:555-564. [PMID: 31025582 DOI: 10.1080/17512433.2019.1612744] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Introduction: New investigations have shown that 'activated' enteric glial cells (EGCs), astrocyte-like cells of the enteric nervous system (ENS), represent a possible extra-CNS trigger point of the neurodegenerative processes in impaired intestinal permeability conditions. The early modulation of enteric glia-mediated neuroinflammation might optimize neuroprotective treatments outcomes currently used in neurodegenerative diseases. Areas covered: We discussed recent clinical and preclinical data existing on the Pubmed database, concerning the glial role in neurodegeneration. We focused on the gut as possible "entrance door" for endoluminal neurotoxic agents that induce neurological impairments during leaky gut conditions. Moreover, we reviewed the paradigmatic studies linking the leaky gut-induced priming of EGCs to the induction of late neurodegenerative processes in Parkinson's disease and other neurodegenerative disorders. Expert opinion: The previous appearance of neuropathological markers in the ENS emphasizes the extra-CNS origin of neurodegenerative disorders, by directing their therapies toward peripheral management of neurodegeneration. In light of the EGCs changes resulting from a switch-on of activated phenotype in leaky gut syndrome, EGCs sampling could be predictive for neuropathological conditions detection, anticipating their symptomatic manifestation in the CNS.
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Affiliation(s)
- Luisa Seguella
- a Department of Physiology and Pharmacology "V. Erspamer" , Sapienza University of Rome , Rome , Italy
| | - Riccardo Capuano
- a Department of Physiology and Pharmacology "V. Erspamer" , Sapienza University of Rome , Rome , Italy
| | - Giovanni Sarnelli
- b Department of Clinical Medicine and Surgery , University of Naples 'Federico II' , Naples , Italy
| | - Giuseppe Esposito
- a Department of Physiology and Pharmacology "V. Erspamer" , Sapienza University of Rome , Rome , Italy
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9
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Ellis CK, Volker SF, Griffin DL, VerCauteren KC, Nichols TA. Use of faecal volatile organic compound analysis for ante-mortem discrimination between CWD-positive, -negative exposed, and -known negative white-tailed deer (Odocoileus virginianus). Prion 2019; 13:94-105. [PMID: 31032718 PMCID: PMC7000150 DOI: 10.1080/19336896.2019.1607462] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 03/26/2019] [Accepted: 04/04/2019] [Indexed: 12/21/2022] Open
Abstract
Chronic wasting disease (CWD) is a naturally occurring infectious, fatal, transmissible spongiform encephalopathy of cervids. Currently, disease confirmation relies on post-mortem detection of infectious prions in the medial retropharyngeal lymph nodes or obex in the brain via immunohistochemistry (IHC). Detection of CWD in living animals using this method is impractical, and IHC and other experimental assays are not reliable in detecting low concentrations of prion present in biofluids or faeces. Here, we evaluate the capability of faecal volatile organic compound analysis to discriminate between CWD-positive and -exposed white-tailed deer located at two positive cervid farms, and two groups of CWD-negative deer from two separate disease-free farms.
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Affiliation(s)
- Christine K. Ellis
- Feral Swine Project, USDA-APHIS-WS-National Wildlife Research Center, Fort Collins, CO, USA
| | - Steven F. Volker
- Analytical Chemistry Department, USDA-APHIS-WS-National Wildlife Research Center, Fort Collins, CO, USA
| | - Doreen L. Griffin
- BioLaboratories, USDA-APHIS-WS-National Wildlife Research Center, Fort Collins, CO, USA
| | - Kurt C. VerCauteren
- Feral Swine Project, USDA-APHIS-WS-National Wildlife Research Center, Fort Collins, CO, USA
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10
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Özbek M, Bozkurt MF, Beyaz F, Ergün E, Ergün L. Expression profile of some neuronal and glial cell markers in the ovine ileal enteric nervous system during prenatal development. Acta Histochem 2018; 120:768-779. [PMID: 30217408 DOI: 10.1016/j.acthis.2018.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/07/2018] [Accepted: 09/03/2018] [Indexed: 02/06/2023]
Abstract
The enteric nervous system (ENS) is a network of neurons and glia found in the gut wall and governs this gastrointestinal function independently from the central nervous system (CNS). ENS comprises the myenteric plexus (MP) and the submucous plexus (SP). In this study, we examined the expression profile of neurofilament heavy chain (NF-H), neuron-specific enolase (NSE), calcyclin (S100A6), vimentin and glial fibril acidic protein (GFAP) in ovine ileal enteric neurons and enteric glia cells (EGCs) during prenatal development using an immunohistochemical method. The material of the study consisted of 15 different fetal ileum tissues obtained between days 60 and 150 of pregnancy. NF-H was observed in the majority of ganglion cells in SP and MP throughout the fetal period. It was determined that there was no NF-H reaction in some ganglion cells in Peyer's patches of internal submucosal plexus (ISPF). In the early stage of pregnancy (60-90 days), there was no expression of NSE and S1006 in ileum. After this period, NSE and S1006 were expressed in the ganglion cells of the plexus, indicating an increase in the amount of expression towards the end of pregnancy. In the early period, vimentin expression was only detected in intramuscular interstitial cells (ICs) (60-90 days), but later (90-150 days) it was also seen in the cells around the ganglion cells in the plexus. On days 60-90 of gestation, GFAP expression only occurred in MP, but in later stages, staining was also detected in SP. In the plexus, an immunoreactivity was present in EGCs forming a network around the ganglion cell. During the last period of gestation (120-150 days), the number of GFAP-positive plexus increased, with the majority of these stained cells being observed in MP. Interestingly, weak staining or reaction did not occur in ISPF, unlike other plexuses. In conclusion, this is the first study that demonstrated the expression of NF-H, vimentin, S100A6, NSE and glial fibril acidic protein (GFAP) in ovine ileal ENS in the prenatal period. In the last period of gestation (120-150 days), the expression profile of ENS was similar to that of adult animals. The expression of the used markers increased toward the end of pregnancy. Our results suggest that neurons and EGCs show heterogeneity, and GFAP and NF-H cannot be used as panenteric glial or panneuronal markers, respectively. We also demonstrated, for the first time, the prenatal expression of S100A6 in enteric neurons and the possibility of using this protein for the identification of enteric neurons.
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Affiliation(s)
- Mehmet Özbek
- Deparment of Histology and Embryology, Faculty of Veterinary Medicine, Mehmet Akif Ersoy University, İstiklal Yerleşkesi, 15030, Burdur, Turkey.
| | - Mehmet Fatih Bozkurt
- Department of Pathology, Faculty of Veterinary Medicine, Afyon Kocatepe University, Afyonkarahisar, Turkey
| | - Feyzullah Beyaz
- Deparment of Histology and Embryology, Faculty of Veterinary Medicine, Erciyes University, Kayseri, Turkey
| | - Emel Ergün
- Deparment of Histology and Embryology, Faculty of Veterinary Medicine, Ankara University, Ankara, Turkey
| | - Levent Ergün
- Deparment of Histology and Embryology, Faculty of Veterinary Medicine, Ankara University, Ankara, Turkey
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11
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Abstract
The interplay between the immune and nervous systems has been acknowledged in the past, but only more recent studies have started to unravel the cellular and molecular players of such interactions. Mounting evidence indicates that environmental signals are sensed by discrete neuro-immune cell units (NICUs), which represent defined anatomical locations in which immune and neuronal cells colocalize and functionally interact to steer tissue physiology and protection. These units have now been described in multiple tissues throughout the body, including lymphoid organs, adipose tissue, and mucosal barriers. As such, NICUs are emerging as important orchestrators of multiple physiological processes, including hematopoiesis, organogenesis, inflammation, tissue repair, and thermogenesis. In this review we focus on the impact of NICUs in tissue physiology and how this fast-evolving field is driving a paradigm shift in our understanding of immunoregulation and organismal physiology.
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Affiliation(s)
- Cristina Godinho-Silva
- Champalimaud Research, Champalimaud Centre for the Unknown, 1400-038 Lisboa, Portugal; , ,
| | - Filipa Cardoso
- Champalimaud Research, Champalimaud Centre for the Unknown, 1400-038 Lisboa, Portugal; , ,
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12
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Assessment of Chronic Wasting Disease Prion Shedding in Deer Saliva with Occupancy Modeling. J Clin Microbiol 2017; 56:JCM.01243-17. [PMID: 29118163 DOI: 10.1128/jcm.01243-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 10/31/2017] [Indexed: 01/06/2023] Open
Abstract
The detection of prions is difficult due to the peculiarity of the pathogen, which is a misfolded form of a normal protein. The specificity and sensitivity of detection methods are imperfect in complex samples, including in excreta. Here, we combined optimized prion amplification procedures with a statistical method that accounts for false-positive and false-negative errors to test deer saliva for chronic wasting disease (CWD) prions. This approach enabled us to discriminate the shedding of prions in saliva and the detection of prions in saliva-a distinction crucial to understanding the role of prion shedding in disease transmission and for diagnosis. We found that assay sensitivity and specificity were indeed imperfect, and we were able to draw several conclusions pertinent to CWD biology from our analyses: (i) the shedding of prions in saliva increases with time postinoculation, but is common throughout the preclinical phase of disease; (ii) the shedding propensity is influenced neither by sex nor by prion protein genotype at codon 96; and (iii) the source of prion-containing inoculum used to infect deer affects the likelihood of prion shedding in saliva; oral inoculation of deer with CWD-positive saliva resulted in 2.77 times the likelihood of prion shedding in saliva compared to that from inoculation with CWD-positive brain. These results are pertinent to horizontal CWD transmission in wild cervids. Moreover, the approach described is applicable to other diagnostic assays with imperfect detection.
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Haley NJ, Richt JA. Evolution of Diagnostic Tests for Chronic Wasting Disease, a Naturally Occurring Prion Disease of Cervids. Pathogens 2017; 6:pathogens6030035. [PMID: 28783058 PMCID: PMC5617992 DOI: 10.3390/pathogens6030035] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/29/2017] [Accepted: 08/01/2017] [Indexed: 12/23/2022] Open
Abstract
Since chronic wasting disease (CWD) was first identified nearly 50 years ago in a captive mule deer herd in the Rocky Mountains of the United States, it has slowly spread across North America through the natural and anthropogenic movement of cervids and their carcasses. As the endemic areas have expanded, so has the need for rapid, sensitive, and cost effective diagnostic tests—especially those which take advantage of samples collected antemortem. Over the past two decades, strategies have evolved from the recognition of microscopic spongiform pathology and associated immunohistochemical staining of the misfolded prion protein to enzyme-linked immunoassays capable of detecting the abnormal prion conformer in postmortem samples. In a history that parallels the diagnosis of more conventional infectious agents, both qualitative and real-time amplification assays have recently been developed to detect minute quantities of misfolded prions in a range of biological and environmental samples. With these more sensitive and semi-quantitative approaches has come a greater understanding of the pathogenesis and epidemiology of this disease in the native host. Because the molecular pathogenesis of prion protein misfolding is broadly analogous to the misfolding of other pathogenic proteins, including Aβ and α-synuclein, efforts are currently underway to apply these in vitro amplification techniques towards the diagnosis of Alzheimer’s disease, Parkinson’s disease, and other proteinopathies. Chronic wasting disease—once a rare disease of Colorado mule deer—now represents one of the most prevalent prion diseases, and should serve as a model for the continued development and implementation of novel diagnostic strategies for protein misfolding disorders in the natural host.
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Affiliation(s)
- Nicholas J Haley
- Department of Microbiology and Immunology, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ 85308, USA.
| | - Jürgen A Richt
- College of Veterinary Medicine, Kansas State University (KSU), Manhattan, KS 66506, USA.
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Ellett LJ, Lawson VA. Preparation and Immunostaining of the Myenteric Plexus of Prion-Infected Mice. Methods Mol Biol 2017; 1658:285-292. [PMID: 28861796 DOI: 10.1007/978-1-4939-7244-9_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Intracerebral inoculation of mice with the M1000 strain of mouse-adapted human prions results in the consistent accumulation of PrPSc in the ileum of the gastrointestinal tract (GIT) of mice with clinical signs of prion disease. The accumulation of PrPSc in the ileum is accompanied by caspase activation and loss of immunoreactivity in subpopulations of neurons in the enteric nervous system. This suggests that like neurons in the central nervous system, cells in the enteric nervous system are also susceptible to prion-induced toxicity. In this chapter we describe the immunostaining of cells in myenteric plexus preparations of whole mounts prepared from the gastrointestinal tract of prion-infected mice.
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Affiliation(s)
- Laura J Ellett
- Department of Pathology, The University of Melbourne, Medical Building, Parkville, VIC, 3010, Australia
| | - Victoria A Lawson
- Department of Pathology, The University of Melbourne, Medical Building, Parkville, VIC, 3010, Australia.
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15
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Holcomb KM, Galloway NL, Mathiason CK, Antolin MF. Intra-host mathematical model of chronic wasting disease dynamics in deer (Odocoileus). Prion 2016; 10:377-390. [PMID: 27537196 PMCID: PMC5105936 DOI: 10.1080/19336896.2016.1189054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Bioassays of native cervid hosts have established the presence of infectious chronic wasting disease (CWD) prions in saliva, blood, urine, and feces of clinically diseased and pre-clinical infected deer. The intra-host trafficking of prions from the time of initial infection to shedding has been less well defined. We created a discrete-time compartmentalized model to simulate the misfolding catalysis, trafficking, and shedding of infectious prions throughout the organ systems of CWD-infected cervids. Using parameter values derived from experimental infections of North American deer (Odocoileus spp.), the exponential-based model predicts prion deposition over time with: 1) nervous tissues containing the highest deposition of prions at 20 months post-infection and 2) excreted fluids containing low levels of prions throughout infection with the highest numbers of prions predicted to be shed in saliva and feces (as high as 10 lethal doses (1.34 × 1029 prions) in 11–15 months). These findings are comparable to prion deposition described in literature as assayed by conventional and ultrasensitive amplification assays. The comparison of our model to published data suggests that highly sensitive assays (sPMCA, RT-QuIC, and bioassay) are appropriate for early prion detection in bodily fluids and secretions. The model provides a view of intra-host prion catalysis leading to pre-clinical shedding and provides a framework for continued development of antemortem diagnostic methods.
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Affiliation(s)
- Karen M Holcomb
- a Department of Biology , Colorado State University , Fort Collins , CO , USA
| | - Nathan L Galloway
- a Department of Biology , Colorado State University , Fort Collins , CO , USA
| | - Candace K Mathiason
- b Department of Microbiology , Immunology, and Pathology, Colorado State University , Fort Collins , CO , USA
| | - Michael F Antolin
- a Department of Biology , Colorado State University , Fort Collins , CO , USA
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16
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Ochoa-Cortes F, Turco F, Linan-Rico A, Soghomonyan S, Whitaker E, Wehner S, Cuomo R, Christofi FL. Enteric Glial Cells: A New Frontier in Neurogastroenterology and Clinical Target for Inflammatory Bowel Diseases. Inflamm Bowel Dis 2016; 22:433-49. [PMID: 26689598 PMCID: PMC4718179 DOI: 10.1097/mib.0000000000000667] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 08/29/2015] [Indexed: 12/12/2022]
Abstract
The word "glia" is derived from the Greek word "γλoια," glue of the enteric nervous system, and for many years, enteric glial cells (EGCs) were believed to provide mainly structural support. However, EGCs as astrocytes in the central nervous system may serve a much more vital and active role in the enteric nervous system, and in homeostatic regulation of gastrointestinal functions. The emphasis of this review will be on emerging concepts supported by basic, translational, and/or clinical studies, implicating EGCs in neuron-to-glial (neuroglial) communication, motility, interactions with other cells in the gut microenvironment, infection, and inflammatory bowel diseases. The concept of the "reactive glial phenotype" is explored as it relates to inflammatory bowel diseases, bacterial and viral infections, postoperative ileus, functional gastrointestinal disorders, and motility disorders. The main theme of this review is that EGCs are emerging as a new frontier in neurogastroenterology and a potential therapeutic target. New technological innovations in neuroimaging techniques are facilitating progress in the field, and an update is provided on exciting new translational studies. Gaps in our knowledge are discussed for further research. Restoring normal EGC function may prove to be an efficient strategy to dampen inflammation. Probiotics, palmitoylethanolamide (peroxisome proliferator-activated receptor-α), interleukin-1 antagonists (anakinra), and interventions acting on nitric oxide, receptor for advanced glycation end products, S100B, or purinergic signaling pathways are relevant clinical targets on EGCs with therapeutic potential.
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Affiliation(s)
| | - Fabio Turco
- Department of Anesthesiology, The Ohio State University, Columbus, Ohio
- Department of Clinical and Experimental Medicine, Gastroenterological Unit, “Federico II” University of Naples, Naples, Italy; and
| | | | - Suren Soghomonyan
- Department of Anesthesiology, The Ohio State University, Columbus, Ohio
| | - Emmett Whitaker
- Department of Anesthesiology, The Ohio State University, Columbus, Ohio
| | - Sven Wehner
- Department of Surgery, University of Bonn, Bonn, Germany
| | - Rosario Cuomo
- Department of Clinical and Experimental Medicine, Gastroenterological Unit, “Federico II” University of Naples, Naples, Italy; and
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Coelho-Aguiar JDM, Bon-Frauches AC, Gomes ALT, Veríssimo CP, Aguiar DP, Matias D, Thomasi BBDM, Gomes AS, Brito GADC, Moura-Neto V. The enteric glia: identity and functions. Glia 2015; 63:921-35. [PMID: 25703790 DOI: 10.1002/glia.22795] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 01/07/2015] [Indexed: 01/04/2023]
Abstract
Enteric glial cells were first described at the end of the 19th century, but they attracted more interest from researchers only in the last decades of the 20th. Although, they have a different embryological origin, the enteric GLIA share many characteristics with astrocytes, the main glial cell type of the central nervous system (CNS), such as in their expression of the same markers and in their functions. Here we review the construction of the enteric nervous system (ENS), with a focus on enteric glia, and also the main studies that have revealed the action of enteric glia in different aspects of gastrointestinal tract homeostasis, such as in the intestinal barrier, in communications with neurons, and in their action as progenitor cells. We also discuss recent discoveries about the roles of enteric glia in different disorders that affect the ENS, such as degenerative pathologies including Parkinson's and prion diseases, and in cases of intestinal diseases and injury.
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Affiliation(s)
- Juliana de Mattos Coelho-Aguiar
- Instituto Estadual do Cérebro Paulo Niemeyer, Secretaria de Estado de Saúde do Rio de Janeiro - SES/RJ, Rio de Janeiro, Brazil; Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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18
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Goñi F, Mathiason CK, Yim L, Wong K, Hayes-Klug J, Nalls A, Peyser D, Estevez V, Denkers N, Xu J, Osborn DA, Miller KV, Warren RJ, Brown DR, Chabalgoity JA, Hoover EA, Wisniewski T. Mucosal immunization with an attenuated Salmonella vaccine partially protects white-tailed deer from chronic wasting disease. Vaccine 2014; 33:726-33. [PMID: 25539804 DOI: 10.1016/j.vaccine.2014.11.035] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 11/13/2014] [Accepted: 11/19/2014] [Indexed: 10/24/2022]
Abstract
Prion disease is a unique category of illness, affecting both animals and humans, in which the underlying pathogenesis is related to a conformational change of a normal, self-protein called PrP(C) (C for cellular) to a pathological and infectious conformer known as PrP(Sc) (Sc for scrapie). Bovine spongiform encephalopathy (BSE), a prion disease believed to have arisen from feeding cattle with prion contaminated meat and bone meal products, crossed the species barrier to infect humans. Chronic wasting disease (CWD) infects large numbers of deer and elk, with the potential to infect humans. Currently no prionosis has an effective treatment. Previously, we have demonstrated we could prevent transmission of prions in a proportion of susceptible mice with a mucosal vaccine. In the current study, white-tailed deer were orally inoculated with attenuated Salmonella expressing PrP, while control deer were orally inoculated with vehicle attenuated Salmonella. Once a mucosal response was established, the vaccinated animals were boosted orally and locally by application of polymerized recombinant PrP onto the tonsils and rectal mucosa. The vaccinated and control animals were then challenged orally with CWD-infected brain homogenate. Three years post CWD oral challenge all control deer developed clinical CWD (median survival 602 days), while among the vaccinated there was a significant prolongation of the incubation period (median survival 909 days; p=0.012 by Weibull regression analysis) and one deer has remained CWD free both clinically and by RAMALT and tonsil biopsies. This negative vaccinate has the highest titers of IgA in saliva and systemic IgG against PrP. Western blots showed that immunoglobulins from this vaccinate react to PrP(CWD). We document the first partially successful vaccination for a prion disease in a species naturally at risk.
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Affiliation(s)
- Fernando Goñi
- Department of Neurology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States
| | - Candace K Mathiason
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Lucia Yim
- Laboratory for Vaccine Research, Department of Biotechnology, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Kinlung Wong
- Department of Neurology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States
| | - Jeanette Hayes-Klug
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Amy Nalls
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Daniel Peyser
- Department of Neurology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States
| | - Veronica Estevez
- Laboratory for Vaccine Research, Department of Biotechnology, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Nathaniel Denkers
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Jinfeng Xu
- Department of Population Health, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States
| | - David A Osborn
- Warnell School of Forestry and Natural Resources, University of Georgia, United States
| | - Karl V Miller
- Warnell School of Forestry and Natural Resources, University of Georgia, United States
| | - Robert J Warren
- Warnell School of Forestry and Natural Resources, University of Georgia, United States
| | - David R Brown
- Department of Biology and Biochemistry, University of Bath, UK
| | - Jose A Chabalgoity
- Laboratory for Vaccine Research, Department of Biotechnology, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Edward A Hoover
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Thomas Wisniewski
- Department of Neurology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States; Department of Pathology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States; Department of Psychiatry, New York University School of Medicine, 550 First Avenue, New York, NY 10016, United States.
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19
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Seelig DM, Nalls AV, Flasik M, Frank V, Eaton S, Mathiason CK, Hoover EA. Lesion profiling and subcellular prion localization of cervid chronic wasting disease in domestic cats. Vet Pathol 2014; 52:107-19. [PMID: 24577721 DOI: 10.1177/0300985814524798] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Chronic wasting disease (CWD) is an efficiently transmitted, fatal, and progressive prion disease of cervids with an as yet to be fully clarified host range. While outbred domestic cats (Felis catus) have recently been shown to be susceptible to experimental CWD infection, the neuropathologic features of the infection are lacking. Such information is vital to provide diagnostic power in the event of natural interspecies transmission and insights into host and strain interactions in interspecies prion infection. Using light microscopy and immunohistochemistry, we detail the topographic pattern of neural spongiosis (the "lesion profile") and the distribution of misfolded prion protein in the primary and secondary passage of feline CWD (Fel(CWD)). We also evaluated cellular and subcellular associations between misfolded prion protein (PrP(D)) and central nervous system neurons and glial cell populations. From these studies, we (1) describe the novel neuropathologic profile of Fel(CWD), which is distinct from either cervid CWD or feline spongiform encephalopathy (FSE), and (2) provide evidence of serial passage-associated interspecies prion adaptation. In addition, we demonstrate through confocal analysis the successful co-localization of PrP(D) with neurons, astrocytes, microglia, lysosomes, and synaptophysin, which, in part, implicates each of these in the neuropathology of Fel(CWD). In conclusion, this work illustrates the simultaneous role of both host and strain in the development of a unique Fel(CWD) neuropathologic profile and that such a profile can be used to discriminate between Fel(CWD) and FSE.
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Affiliation(s)
- D M Seelig
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - A V Nalls
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - M Flasik
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - V Frank
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - S Eaton
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - C K Mathiason
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - E A Hoover
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
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Abstract
Domestic and nondomestic cats have been shown to be susceptible to feline spongiform encephalopathy (FSE), almost certainly caused by consumption of bovine spongiform encephalopathy (BSE)-contaminated meat. Because domestic and free-ranging nondomestic felids scavenge cervid carcasses, including those in areas affected by chronic wasting disease (CWD), we evaluated the susceptibility of the domestic cat (Felis catus) to CWD infection experimentally. Cohorts of 5 cats each were inoculated intracerebrally (i.c.) or orally (p.o.) with CWD-infected deer brain. At 40 and 42 months postinoculation, two i.c.-inoculated cats developed signs consistent with prion disease, including a stilted gait, weight loss, anorexia, polydipsia, patterned motor behaviors, head and tail tremors, and ataxia, and the cats progressed to terminal disease within 5 months. Brains from these two cats were pooled and inoculated into cohorts of cats by the i.c., p.o., and intraperitoneal and subcutaneous (i.p./s.c.) routes. Upon subpassage, feline CWD was transmitted to all i.c.-inoculated cats with a decreased incubation period of 23 to 27 months. Feline-adapted CWD (Fel(CWD)) was demonstrated in the brains of all of the affected cats by Western blotting and immunohistochemical analysis. Magnetic resonance imaging revealed abnormalities in clinically ill cats, which included multifocal T2 fluid attenuated inversion recovery (FLAIR) signal hyperintensities, ventricular size increases, prominent sulci, and white matter tract cavitation. Currently, 3 of 4 i.p./s.c.- and 2 of 4 p.o. secondary passage-inoculated cats have developed abnormal behavior patterns consistent with the early stage of feline CWD. These results demonstrate that CWD can be transmitted and adapted to the domestic cat, thus raising the issue of potential cervid-to-feline transmission in nature.
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Sharkey KA. Tyrosine hydroxylase in the stalk-median eminence and posterior pituitary is inactivated only during the plateau phase of the preovulatory prolactin surge. Endocrinology 1989; 125:918-25. [PMID: 25689252 DOI: 10.1172/jci76303] [Citation(s) in RCA: 135] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This study examined changes in the activity of tyrosine hydroxylase (TH) in the stalk-median eminence (SME) and posterior pituitary (PP) during the preovulatory PRL surge. Immature female rats were injected with PMSG on day 28. Blood PRL levels were low on the morning of day 30, rose to a peak from 1400-1600 h, remained at a lower plateau from 1800-2400 h, and declined to basal levels on the morning of day 31. SME, PP, and striatum were removed from PMSG-treated rats at selected times during the periovulatory period and from age-matched control rats. TH activity was determined in tissue homogenates by a coupled hydroxylation-decarboxylation assay. Apparent Km and maximum velocity values with respect to 6-methyl tetrahydropterine were estimated from substrate saturation curves. The kinetic parameters for TH in either the SME or the PP of control rats were similar at 1100 and 1800 h on day 30. However, the apparent Km in both tissues was significantly lower than that in the striatum. The affinity of TH in the SME and PP was unchanged before and during the peak phase of the PRL surge, reduced significantly during the late plateau, and returned to presurge levels in the morning of day 31. TH activity in the striatum was similar at all times examined. To determine the state of activation of the enzyme, tissue homogenates were preincubated with cAMP, ATP, and magnesium. TH activity in the SME during the peak phase was unchanged by cAMP, and that in the PP was modestly increased. The relatively inactive enzyme in both tissues during the plateau phase was markedly activated by a cAMP-dependent mechanism. The low affinity of striatal TH was greatly increased by cAMP at both times. These data suggest that TH in the SME and PP exists in an activated state most of the time and is transiently inactivated during the plateau phase of the PRL surge. In contrast, TH in the striatum is relatively inactive in the basal state and is not affected by hormonal changes induced by PMSG. We conclude that the peak PRL surge occurs in spite of active dopamine (DA) neurons, suggesting that it is generated by a nondopaminergic mechanism. Decreased TH activity in DA neurons in the SME and PP may prolong the PRL surge during the plateau phase, whereas increased DA activity coincides with the termination of the surge.
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