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Jackson RJ, Hyman BT, Serrano-Pozo A. Multifaceted roles of APOE in Alzheimer disease. Nat Rev Neurol 2024:10.1038/s41582-024-00988-2. [PMID: 38906999 DOI: 10.1038/s41582-024-00988-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2024] [Indexed: 06/23/2024]
Abstract
For the past three decades, apolipoprotein E (APOE) has been known as the single greatest genetic modulator of sporadic Alzheimer disease (AD) risk, influencing both the average age of onset and the lifetime risk of developing AD. The APOEε4 allele significantly increases AD risk, whereas the ε2 allele is protective relative to the most common ε3 allele. However, large differences in effect size exist across ethnoracial groups that are likely to depend on both global genetic ancestry and local genetic ancestry, as well as gene-environment interactions. Although early studies linked APOE to amyloid-β - one of the two culprit aggregation-prone proteins that define AD - in the past decade, mounting work has associated APOE with other neurodegenerative proteinopathies and broader ageing-related brain changes, such as neuroinflammation, energy metabolism failure, loss of myelin integrity and increased blood-brain barrier permeability, with potential implications for longevity and resilience to pathological protein aggregates. Novel mouse models and other technological advances have also enabled a number of therapeutic approaches aimed at either attenuating the APOEε4-linked increased AD risk or enhancing the APOEε2-linked AD protection. This Review summarizes this progress and highlights areas for future research towards the development of APOE-directed therapeutics.
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Jackson RJ, Keiser MS, Meltzer JC, Fykstra DP, Dierksmeier SE, Hajizadeh S, Kreuzer J, Morris R, Melloni A, Nakajima T, Tecedor L, Ranum PT, Carrell E, Chen Y, Nishtar MA, Holtzman DM, Haas W, Davidson BL, Hyman BT. APOE2 gene therapy reduces amyloid deposition and improves markers of neuroinflammation and neurodegeneration in a mouse model of Alzheimer disease. Mol Ther 2024; 32:1373-1386. [PMID: 38504517 PMCID: PMC11081918 DOI: 10.1016/j.ymthe.2024.03.024] [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: 07/17/2023] [Revised: 01/05/2024] [Accepted: 03/15/2024] [Indexed: 03/21/2024] Open
Abstract
Epidemiological studies show that individuals who carry the relatively uncommon APOE ε2 allele rarely develop Alzheimer disease, and if they do, they have a later age of onset, milder clinical course, and less severe neuropathological findings than people without this allele. The contrast is especially stark when compared with the major genetic risk factor for Alzheimer disease, APOE ε4, which has an age of onset several decades earlier, a more aggressive clinical course and more severe neuropathological findings, especially in terms of the amount of amyloid deposition. Here, we demonstrate that brain exposure to APOE ε2 via a gene therapy approach, which bathes the entire cortical mantle in the gene product after transduction of the ependyma, reduces Aβ plaque deposition, neurodegenerative synaptic loss, and, remarkably, reduces microglial activation in an APP/PS1 mouse model despite continued expression of human APOE ε4. This result suggests a promising protective effect of exogenous APOE ε2 and reveals a cell nonautonomous effect of the protein on microglial activation, which we show is similar to plaque-associated microglia in the brain of Alzheimer disease patients who inherit APOE ε2. These data increase the potential that an APOE ε2 therapeutic could be effective in Alzheimer disease, even in individuals born with the risky ε4 allele.
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Colom-Cadena M, Toombs J, Simzer E, Holt K, McGeachan R, Tulloch J, Jackson RJ, Catterson JH, Spires-Jones MP, Rose J, Waybright L, Caggiano AO, King D, Gobbo F, Davies C, Hooley M, Dunnett S, Tempelaar R, Meftah S, Tzioras M, Hamby ME, Izzo NJ, Catalano SM, Durrant CS, Smith C, Dando O, Spires-Jones TL. Transmembrane protein 97 is a potential synaptic amyloid beta receptor in human Alzheimer's disease. Acta Neuropathol 2024; 147:32. [PMID: 38319380 PMCID: PMC10847197 DOI: 10.1007/s00401-023-02679-6] [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: 08/09/2023] [Revised: 12/24/2023] [Accepted: 12/24/2023] [Indexed: 02/07/2024]
Abstract
Synapse loss correlates with cognitive decline in Alzheimer's disease, and soluble oligomeric amyloid beta (Aβ) is implicated in synaptic dysfunction and loss. An important knowledge gap is the lack of understanding of how Aβ leads to synapse degeneration. In particular, there has been difficulty in determining whether there is a synaptic receptor that binds Aβ and mediates toxicity. While many candidates have been observed in model systems, their relevance to human AD brain remains unknown. This is in part due to methodological limitations preventing visualization of Aβ binding at individual synapses. To overcome this limitation, we combined two high resolution microscopy techniques: array tomography and Förster resonance energy transfer (FRET) to image over 1 million individual synaptic terminals in temporal cortex from AD (n = 11) and control cases (n = 9). Within presynapses and post-synaptic densities, oligomeric Aβ generates a FRET signal with transmembrane protein 97. Further, Aβ generates a FRET signal with cellular prion protein, and post-synaptic density 95 within post synapses. Transmembrane protein 97 is also present in a higher proportion of post synapses in Alzheimer's brain compared to controls. We inhibited Aβ/transmembrane protein 97 interaction in a mouse model of amyloidopathy by treating with the allosteric modulator CT1812. CT1812 drug concentration correlated negatively with synaptic FRET signal between transmembrane protein 97 and Aβ. In human-induced pluripotent stem cell derived neurons, transmembrane protein 97 is present in synapses and colocalizes with Aβ when neurons are challenged with human Alzheimer's brain homogenate. Transcriptional changes are induced by Aβ including changes in genes involved in neurodegeneration and neuroinflammation. CT1812 treatment of these neurons caused changes in gene sets involved in synaptic function. These data support a role for transmembrane protein 97 in the synaptic binding of Aβ in human Alzheimer's disease brain where it may mediate synaptotoxicity.
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Jackson RJ, Keiser MS, Meltzer JC, Fykstra DP, Dierksmeier SE, Melloni A, Nakajima T, Tecedor L, Ranum PT, Carrell E, Chen Y, Holtzman DM, Davidson BL, Hyman BT. APOE2 gene therapy reduces amyloid deposition, and improves markers of neuroinflammation and neurodegeneration in a mouse model of Alzheimer disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.14.552850. [PMID: 37645718 PMCID: PMC10461997 DOI: 10.1101/2023.08.14.552850] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Epidemiological studies show that individuals who carry the relatively uncommon APOE ε2 allele rarely develop Alzheimer disease, and if they do they have a later age of onset, milder clinical course, and less severe neuropathological findings than others with Alzheimer disease. The contrast is especially stark in comparison to the phenotype associated with the major genetic risk factor for Alzheimer disease, APOE ε4, which has an age of onset several decades earlier, as well as a more aggressive clinical course and notably more severe neuropathological findings, especially in terms of the amount of amyloid deposition. Even one APOE ε2 allele improves phenotype, but it is uncertain if that is due to the replacement of a more toxic allele by APOE ε2, or if APOE ε2 has a protective, neuro-modulatory effect. Here, we demonstrate that brain exposure to APOE2 via a gene therapy approach which bathes the entire cortical mantle in the gene product after transduction of the ependyma, rapidly ameliorates established Aβ plaque deposition, neurodegenerative synaptic loss, and, remarkably, reduces microglial activation in an APP/PS1 mouse model despite continued expression of human APOE4. This result suggests a promising protective effect of exogenous APOE2, revealing a cell non-autonomous effect of the protein on microglial activation. We also show that plaque associated microglia in the brain of patients who inherit APOE2 similarly have less microglial reactivity to plaques. These data raise the potential that an APOE2 therapeutic could be effective in Alzheimer disease even in individuals born with the risk ε4 allele. One Sentence Summary Introduction of ApoE2 using an AAV that transduces the ependymal cells of the ventricle causes a reduction in amyloid load and plaque associated synapse loss, and reduces neuroinflammation by modulating microglial responsiveness to plaques.
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Jackson RJ, Meltzer JC, Nguyen H, Commins C, Bennett RE, Hudry E, Hyman BT. APOE4 derived from astrocytes leads to blood-brain barrier impairment. Brain 2021; 145:3582-3593. [PMID: 34957486 PMCID: PMC9586546 DOI: 10.1093/brain/awab478] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 10/25/2021] [Accepted: 12/01/2021] [Indexed: 02/04/2023] Open
Abstract
Apolipoprotein E (ApoE) is a multifaceted secreted molecule synthesized in the CNS by astrocytes and microglia, and in the periphery largely by the liver. ApoE has been shown to impact the integrity of the blood-brain barrier, and, in humans, the APOE4 allele of the gene is reported to lead to a leaky blood-brain barrier. We used allele specific knock-in mice expressing each of the common (human) ApoE alleles, and longitudinal multiphoton intravital microscopy, to directly monitor the impact of various ApoE isoforms on blood-brain barrier integrity. We found that humanized APOE4, but not APOE2 or APOE3, mice show a leaky blood-brain barrier, increased MMP9, impaired tight junctions, and reduced astrocyte end-foot coverage of blood vessels. Removal of astrocyte-produced ApoE4 led to the amelioration of all phenotypes while the removal of astrocyte-produced ApoE3 had no effect on blood-brain barrier integrity. This work shows a cell specific gain of function effect of ApoE4 in the dysfunction of the BBB and implicates astrocyte production of ApoE4, possibly as a function of astrocytic end foot interactions with vessels, as a key regulator of the integrity of the blood-brain barrier.
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Serrano-Pozo A, Li Z, Noori A, Nguyen HN, Mezlini A, Li L, Hudry E, Jackson RJ, Hyman BT, Das S. Effect of APOE alleles on the glial transcriptome in normal aging and Alzheimer's disease. NATURE AGING 2021; 1:919-931. [PMID: 36199750 PMCID: PMC9531903 DOI: 10.1038/s43587-021-00123-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 09/03/2021] [Indexed: 05/02/2023]
Abstract
The roles of APOEε4 and APOEε2-the strongest genetic risk and protective factors for Alzheimer's disease-in glial responses remain elusive. We tested the hypothesis that APOE alleles differentially impact glial responses by investigating their effects on the glial transcriptome from elderly control brains with no neuritic amyloid plaques. We identified a cluster of microglial genes that are upregulated in APOEε4 and downregulated in APOEε2 carriers relative to APOEε3 homozygotes. This microglia-APOE cluster is enriched in phagocytosis-including TREM2 and TYROBP-and proinflammatory genes, and is also detectable in brains with frequent neuritic plaques. Next, we tested these findings in APOE knock-in mice exposed to acute (lipopolysaccharide challenge) and chronic (cerebral β-amyloidosis) insults and found that these mice partially recapitulate human APOE-linked expression patterns. Thus, the APOEε4 allele might prime microglia towards a phagocytic and proinflammatory state through an APOE-TREM2-TYROBP axis in normal aging as well as in Alzheimer's disease.
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Litvinchuk A, Huynh TPV, Shi Y, Jackson RJ, Finn MB, Manis M, Francis CM, Tran A, Sullivan PM, Ulrich JD, Hyman BT, Cole T, Holtzman DM. Apolipoprotein E4 Reduction with Antisense Oligonucleotides Decreases Neurodegeneration in a Tauopathy Model. Ann Neurol 2021; 89:952-966. [PMID: 33550655 PMCID: PMC8260038 DOI: 10.1002/ana.26043] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 01/23/2021] [Accepted: 01/31/2021] [Indexed: 01/07/2023]
Abstract
OBJECTIVE Apolipoprotein E (ApoE) genotype is the strongest genetic risk factor for late-onset Alzheimer's disease, with the ε4 allele increasing risk in a dose-dependent fashion. In addition to ApoE4 playing a crucial role in amyloid-β deposition, recent evidence suggests that it also plays an important role in tau pathology and tau-mediated neurodegeneration. It is not known, however, whether therapeutic reduction of ApoE4 would exert protective effects on tau-mediated neurodegeneration. METHODS Herein, we used antisense oligonucleotides (ASOs) against human APOE to reduce ApoE4 levels in the P301S/ApoE4 mouse model of tauopathy. We treated P301S/ApoE4 mice with ApoE or control ASOs via intracerebroventricular injection at 6 and 7.5 months of age and performed brain pathological assessments at 9 months of age. RESULTS Our results indicate that treatment with ApoE ASOs reduced ApoE4 protein levels by ~50%, significantly protected against tau pathology and associated neurodegeneration, decreased neuroinflammation, and preserved synaptic density. These data were also corroborated by a significant reduction in levels of neurofilament light chain (NfL) protein in plasma of ASO-treated mice. INTERPRETATION We conclude that reducing ApoE4 levels should be explored further as a therapeutic approach for APOE4 carriers with tauopathy including Alzheimer's disease. ANN NEUROL 2021;89:952-966.
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Hesse R, Hurtado ML, Jackson RJ, Eaton SL, Herrmann AG, Colom-Cadena M, Tzioras M, King D, Rose J, Tulloch J, McKenzie CA, Smith C, Henstridge CM, Lamont D, Wishart TM, Spires-Jones TL. Comparative profiling of the synaptic proteome from Alzheimer's disease patients with focus on the APOE genotype. Acta Neuropathol Commun 2019; 7:214. [PMID: 31862015 PMCID: PMC6925519 DOI: 10.1186/s40478-019-0847-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 11/13/2019] [Indexed: 12/13/2022] Open
Abstract
Degeneration of synapses in Alzheimer's disease (AD) strongly correlates with cognitive decline, and synaptic pathology contributes to disease pathophysiology. We recently observed that the strongest genetic risk factor for sporadic AD, apolipoprotein E epsilon 4 (APOE4), is associated with exacerbated synapse loss and synaptic accumulation of oligomeric amyloid beta in human AD brain. To begin to understand the molecular cascades involved in synapse loss in AD and how this is mediated by APOE, and to generate a resource of knowledge of changes in the synaptic proteome in AD, we conducted a proteomic screen and systematic in silico analysis of synaptoneurosome preparations from temporal and occipital cortices of human AD and control subjects with known APOE gene status. We examined brain tissue from 33 subjects (7-10 per group). We pooled tissue from all subjects in each group for unbiased proteomic analyses followed by validation with individual case samples. Our analysis identified over 5500 proteins in human synaptoneurosomes and highlighted disease, brain region, and APOE-associated changes in multiple molecular pathways including a decreased abundance in AD of proteins important for synaptic and mitochondrial function and an increased abundance of proteins involved in neuroimmune interactions and intracellular signaling.
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Pickett EK, Herrmann AG, McQueen J, Abt K, Dando O, Tulloch J, Jain P, Dunnett S, Sohrabi S, Fjeldstad MP, Calkin W, Murison L, Jackson RJ, Tzioras M, Stevenson A, d'Orange M, Hooley M, Davies C, Colom-Cadena M, Anton-Fernandez A, King D, Oren I, Rose J, McKenzie CA, Allison E, Smith C, Hardt O, Henstridge CM, Hardingham GE, Spires-Jones TL. Amyloid Beta and Tau Cooperate to Cause Reversible Behavioral and Transcriptional Deficits in a Model of Alzheimer's Disease. Cell Rep 2019; 29:3592-3604.e5. [PMID: 31825838 PMCID: PMC6915767 DOI: 10.1016/j.celrep.2019.11.044] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 08/16/2019] [Accepted: 11/11/2019] [Indexed: 02/08/2023] Open
Abstract
A key knowledge gap blocking development of effective therapeutics for Alzheimer's disease (AD) is the lack of understanding of how amyloid beta (Aβ) peptide and pathological forms of the tau protein cooperate in causing disease phenotypes. Within a mouse tau-deficient background, we probed the molecular, cellular, and behavioral disruption triggered by the influence of wild-type human tau on human Aβ-induced pathology. We find that Aβ and tau work cooperatively to cause a hyperactivity behavioral phenotype and to cause downregulation of transcription of genes involved in synaptic function. In both our mouse model and human postmortem tissue, we observe accumulation of pathological tau in synapses, supporting the potential importance of synaptic tau. Importantly, tau reduction in the mice initiated after behavioral deficits emerge corrects behavioral deficits, reduces synaptic tau levels, and substantially reverses transcriptional perturbations, suggesting that lowering synaptic tau levels may be beneficial in AD.
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Li Z, Jackson RJ, Ranasinghe C. A hierarchical role of IL-25 in ILC development and function at the lung mucosae following viral-vector vaccination. Vaccine X 2019; 2:100035. [PMID: 31384749 PMCID: PMC6668243 DOI: 10.1016/j.jvacx.2019.100035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/30/2019] [Accepted: 07/06/2019] [Indexed: 12/22/2022] Open
Abstract
This study demonstrates that modulation of IL-25 and IL-33 cytokines responsible for innate lymphoid cell 2 (ILC2) activation/function can differentially regulate ILC profiles at the vaccination site, in a vaccine route-dependent manner. Specifically, recombinant fowlpox (rFPV) vector-based vaccine co-expressing an adjuvant that transiently sequestered IL-25 (FPV-HIV-IL-25 binding protein), delivered intramuscularly (i.m.) was able to induce significantly lower IL-25R+ ILC2-deived IL-13 and ILC1/ILC3-derived IFN-γ expression with significantly elevated IL-17A in muscle. In contrast, intranasal (i.n.) delivery was able to induce all three known ILC2 subsets (ST2/IL-33R+, IL-25R+, and TSLPR+ ILC2) to express varying amounts of IL-13 in lung, and also the TSLPR+ ILC2 to express IL-4, unlike the unadjuvanted control, which only showed ST2/IL-33R+ ILC2 to express IL-13. Interestingly, the sequestration of IL-25 in lung also induced a unique lineage− ST2/IL-33R− IL-25R− TSLPR− ILC2 population to express elevated IL-13 and IL-4. Moreover, both i.m. and, i.n. FPV-HIV-IL-25BP vaccination induced significantly elevated ILC1/ILC3-derived IL-17A in lung, indicating that ILC2 could directly impact ILC1/ILC3 activity. To our surprise, transient sequestration of IL-33 at the lung mucosae did not alter the lung ILC2 profiles or activity. These inhibitor studies showed that in the context of i.n. viral vector vaccination, IL-25 plays a predominant role in early ILC development/regulation than IL-33, and likely acts as a master regulator of ILC. Our previous findings have indicated that level of IL-4/IL-13 at the vaccination site impacts the quality/avidity of T cell immunity. Taken together data suggest that IL-25 binding protein could be used as an effective i.m. not an i.n. adjuvant to enhance quality of vaccine-specific T cell immunity. These findings evoke the notion that route-dependent manipulation of ILCs according to the target pathogen could be exploited to design more effective vaccines against chronic pathogens in the future.
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Jackson RJ, Rose J, Tulloch J, Henstridge C, Smith C, Spires-Jones TL. Clusterin accumulates in synapses in Alzheimer's disease and is increased in apolipoprotein E4 carriers. Brain Commun 2019; 1:fcz003. [PMID: 31853523 PMCID: PMC6904249 DOI: 10.1093/braincomms/fcz003] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 06/03/2019] [Accepted: 06/10/2019] [Indexed: 12/23/2022] Open
Abstract
One of the major challenges in developing effective therapeutic strategies for Alzheimer’s disease is understanding how genetic risk factors contribute to neurodegeneration. The apolipoprotein epsilon 4 isoform (APOE4) and variants in the Clusterin (CLU) gene (also known as apolipoprotein J) are associated with increased risk of developing Alzheimer’s. Our previous work demonstrated that APOE4 exacerbates synapse degeneration and synaptic accumulation of toxic oligomeric amyloid beta in human Alzheimer’s and mouse models of disease. Here, we observe clusterin in synapses in human Alzheimer's disease brain. The percentage of synapses containing clusterin is higher in APOE4 carriers than APOE3 carriers. Furthermore, we observe oligomeric amyloid beta accumulation within synapses containing clusterin which is also higher in APOE4 carriers. These data link two genetic risk factors with synapse degeneration in Alzheimer’s and support a potential role for clusterin working with APOE in causing synaptic damage.
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Roy S, Jaeson MI, Li Z, Mahboob S, Jackson RJ, Grubor-Bauk B, Wijesundara DK, Gowans EJ, Ranasinghe C. Viral vector and route of administration determine the ILC and DC profiles responsible for downstream vaccine-specific immune outcomes. Vaccine 2019; 37:1266-1276. [PMID: 30733092 DOI: 10.1016/j.vaccine.2019.01.045] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 01/08/2019] [Accepted: 01/23/2019] [Indexed: 12/19/2022]
Abstract
This study demonstrates that route and viral vector can significantly influence the innate lymphoid cells (ILC) and dendritic cells (DC) recruited to the vaccination site, 24 h post delivery. Intranasal (i.n.) vaccination induced ST2/IL-33R+ ILC2, whilst intramuscular (i.m.) induced IL-25R+ and TSLPR+ (Thymic stromal lymphopoietin protein receptor) ILC2 subsets. However, in muscle a novel ILC subset devoid of the known ILC2 markers (IL-25R- IL-33R- TSLPR-) were found to express IL-13, unlike in lung. Different viral vectors also influenced the ILC-derived cytokines and the DC profiles at the respective vaccination sites. Both i.n. and i.m. recombinant fowlpox virus (rFPV) priming, which has been associated with induction of high avidity T cells and effective antibody differentiation exhibited low ILC2-derived IL-13, high NKp46+ ILC1/ILC3 derived IFN-γ and low IL-17A, together with enhanced CD11b+ CD103- conventional DCs (cDC). In contrast, recombinant Modified Vaccinia Ankara (rMVA) and Influenza A vector priming, which has been linked to low avidity T cells, induced opposing ILC derived-cytokine profiles and enhanced cross-presenting DCs. These observations suggested that the former ILC/DC profiles could be a predictor of a balanced cellular and humoral immune outcome. In addition, following i.n. delivery Rhinovirus (RV) and Adenovius type 5 (Ad5) vectors that induced elevated ILC2-derived IL-13, NKp46+ ILC1/ILC3-derived-IFN-γ and no IL-17A, predominantly recruited CD11b- B220+ plasmacytoid DCs (pDC). Knowing that pDC are involved in antibody differentiation, we postulate that i.n. priming with these vectors may favour induction of effective humoral immunity. Our data also revealed that vector-specific replication status and/or presence or absence of immune evasive genes can significantly alter the ILC and DC activity. Collectively, our findings suggest that understanding the route- and vector-specific ILC and DC profiles at the vaccination site may help tailor/design more efficacious viral vector-based vaccines, according to the pathogen of interest.
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Hesse R, von Einem B, Wagner F, Bott P, Schwanzar D, Jackson RJ, Föhr KJ, Lausser L, Kroker KS, Proepper C, Walther P, Kestler HA, Spires-Jones TL, Boeckers T, Rosenbrock H, von Arnim CAF. sAPPβ and sAPPα increase structural complexity and E/I input ratio in primary hippocampal neurons and alter Ca 2+ homeostasis and CREB1-signaling. Exp Neurol 2018; 304:1-13. [PMID: 29466703 DOI: 10.1016/j.expneurol.2018.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 02/09/2018] [Accepted: 02/14/2018] [Indexed: 12/23/2022]
Abstract
One major pathophysiological hallmark of Alzheimer's disease (AD) is senile plaques composed of amyloid β (Aβ). In the amyloidogenic pathway, cleavage of the amyloid precursor protein (APP) is shifted towards Aβ production and soluble APPβ (sAPPβ) levels. Aβ is known to impair synaptic function; however, much less is known about the physiological functions of sAPPβ. The neurotrophic properties of sAPPα, derived from the non-amyloidogenic pathway of APP cleavage, are well-established, whereas only a few, conflicting studies on sAPPβ exist. The intracellular pathways of sAPPβ are largely unknown. Since sAPPβ is generated alongside Aβ by β-secretase (BACE1) cleavage, we tested the hypothesis that sAPPβ effects differ from sAPPα effects as a neurotrophic factor. We therefore performed a head-to-head comparison of both mammalian recombinant peptides in developing primary hippocampal neurons (PHN). We found that sAPPα significantly increases axon length (p = 0.0002) and that both sAPPα and sAPPβ increase neurite number (p < 0.0001) of PHN at 7 days in culture (DIV7) but not at DIV4. Moreover, both sAPPα- and sAPPβ-treated neurons showed a higher neuritic complexity in Sholl analysis. The number of glutamatergic synapses (p < 0.0001), as well as layer thickness of postsynaptic densities (PSDs), were significantly increased, and GABAergic synapses decreased upon sAPP overexpression in PHN. Furthermore, we showed that sAPPα enhances ERK and CREB1 phosphorylation upon glutamate stimulation at DIV7, but not DIV4 or DIV14. These neurotrophic effects are further associated with increased glutamate sensitivity and CREB1-signaling. Finally, we found that sAPPα levels are significantly reduced in brain homogenates of AD patients compared to control subjects. Taken together, our data indicate critical stage-dependent roles of sAPPs in the developing glutamatergic system in vitro, which might help to understand deleterious consequences of altered APP shedding in AD patients, beyond Aβ pathophysiology.
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Xu C, Yu L, Hou J, Jackson RJ, Wang H, Huang C, Liu T, Wang Q, Zou X, Morris RG, Spires-Jones TL, Yang Z, Yin Z, Xu Y, Chen G. Conditional Deletion of PDK1 in the Forebrain Causes Neuron Loss and Increased Apoptosis during Cortical Development. Front Cell Neurosci 2017; 11:330. [PMID: 29104535 PMCID: PMC5655024 DOI: 10.3389/fncel.2017.00330] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 10/05/2017] [Indexed: 12/26/2022] Open
Abstract
Decreased expression but increased activity of PDK1 has been observed in neurodegenerative disease. To study in vivo function of PDK1 in neuron survival during cortical development, we generate forebrain-specific PDK1 conditional knockout (cKO) mice. We demonstrate that PDK1 cKO mice display striking neuron loss and increased apoptosis. We report that PDK1 cKO mice exhibit deficits on several behavioral tasks. Moreover, PDK1 cKO mice show decreased activities for Akt and mTOR. These results highlight an essential role of endogenous PDK1 in the maintenance of neuronal survival during cortical development.
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Ritchie DL, Adlard P, Peden AH, Lowrie S, Le Grice M, Burns K, Jackson RJ, Yull H, Keogh MJ, Wei W, Chinnery PF, Head MW, Ironside JW. Amyloid-β accumulation in the CNS in human growth hormone recipients in the UK. Acta Neuropathol 2017; 134:221-240. [PMID: 28349199 PMCID: PMC5508038 DOI: 10.1007/s00401-017-1703-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 03/15/2017] [Accepted: 03/18/2017] [Indexed: 12/31/2022]
Abstract
Human-to-human transmission of Creutzfeldt-Jakob disease (CJD) has occurred through medical procedures resulting in iatrogenic CJD (iCJD). One of the commonest causes of iCJD was the use of human pituitary-derived growth hormone (hGH) to treat primary or secondary growth hormone deficiency. As part of a comprehensive tissue-based analysis of the largest cohort yet collected (35 cases) of UK hGH-iCJD cases, we describe the clinicopathological phenotype of hGH-iCJD in the UK. In the 33/35 hGH-iCJD cases with sufficient paraffin-embedded tissue for full pathological examination, we report the accumulation of the amyloid beta (Aβ) protein associated with Alzheimer's disease (AD) in the brains and cerebral blood vessels in 18/33 hGH-iCJD patients and for the first time in 5/12 hGH recipients who died from causes other than CJD. Aβ accumulation was markedly less prevalent in age-matched patients who died from sporadic CJD and variant CJD. These results are consistent with the hypothesis that Aβ, which can accumulate in the pituitary gland, was present in the inoculated hGH preparations and had a seeding effect in the brains of around 50% of all hGH recipients, producing an AD-like neuropathology and cerebral amyloid angiopathy (CAA), regardless of whether CJD neuropathology had occurred. These findings indicate that Aβ seeding can occur independently and in the absence of the abnormal prion protein in the human brain. Our findings provide further evidence for the prion-like seeding properties of Aβ and give insights into the possibility of iatrogenic transmission of AD and CAA.
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Zhou L, McInnes J, Wierda K, Holt M, Herrmann AG, Jackson RJ, Wang YC, Swerts J, Beyens J, Miskiewicz K, Vilain S, Dewachter I, Moechars D, De Strooper B, Spires-Jones TL, De Wit J, Verstreken P. Tau association with synaptic vesicles causes presynaptic dysfunction. Nat Commun 2017; 8:15295. [PMID: 28492240 PMCID: PMC5437271 DOI: 10.1038/ncomms15295] [Citation(s) in RCA: 224] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 03/17/2017] [Indexed: 12/18/2022] Open
Abstract
Tau is implicated in more than 20 neurodegenerative diseases, including Alzheimer's disease. Under pathological conditions, Tau dissociates from axonal microtubules and missorts to pre- and postsynaptic terminals. Patients suffer from early synaptic dysfunction prior to Tau aggregate formation, but the underlying mechanism is unclear. Here we show that pathogenic Tau binds to synaptic vesicles via its N-terminal domain and interferes with presynaptic functions, including synaptic vesicle mobility and release rate, lowering neurotransmission in fly and rat neurons. Pathological Tau mutants lacking the vesicle binding domain still localize to the presynaptic compartment but do not impair synaptic function in fly neurons. Moreover, an exogenously applied membrane-permeable peptide that competes for Tau-vesicle binding suppresses Tau-induced synaptic toxicity in rat neurons. Our work uncovers a presynaptic role of Tau that may be part of the early pathology in various Tauopathies and could be exploited therapeutically.
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Jackson RJ, Rudinskiy N, Herrmann AG, Croft S, Kim JM, Petrova V, Ramos-Rodriguez JJ, Pitstick R, Wegmann S, Garcia-Alloza M, Carlson GA, Hyman BT, Spires-Jones TL. Human tau increases amyloid β plaque size but not amyloid β-mediated synapse loss in a novel mouse model of Alzheimer's disease. Eur J Neurosci 2016; 44:3056-3066. [PMID: 27748574 PMCID: PMC5215483 DOI: 10.1111/ejn.13442] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 09/21/2016] [Accepted: 10/13/2016] [Indexed: 11/28/2022]
Abstract
Alzheimer's disease is characterized by the presence of aggregates of amyloid beta (Aβ) in senile plaques and tau in neurofibrillary tangles, as well as marked neuron and synapse loss. Of these pathological changes, synapse loss correlates most strongly with cognitive decline. Synapse loss occurs prominently around plaques due to accumulations of oligomeric Aβ. Recent evidence suggests that tau may also play a role in synapse loss but the interactions of Aβ and tau in synapse loss remain to be determined. In this study, we generated a novel transgenic mouse line, the APP/PS1/rTg21221 line, by crossing APP/PS1 mice, which develop Aβ‐plaques and synapse loss, with rTg21221 mice, which overexpress wild‐type human tau. When compared to the APP/PS1 mice without human tau, the cross‐sectional area of ThioS+ dense core plaques was increased by ~50%. Along with increased plaque size, we observed an increase in plaque‐associated dystrophic neurites containing misfolded tau, but there was no exacerbation of neurite curvature or local neuron loss around plaques. Array tomography analysis similarly revealed no worsening of synapse loss around plaques, and no change in the accumulation of Aβ at synapses. Together, these results indicate that adding human wild‐type tau exacerbates plaque pathology and neurite deformation but does not exacerbate plaque‐associated synapse loss.
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Henstridge CM, Jackson RJ, Kim JM, Herrmann AG, Wright AK, Harris SE, Bastin ME, Starr JM, Wardlaw J, Gillingwater TH, Smith C, McKenzie CA, Cox SR, Deary IJ, Spires-Jones TL. Post-mortem brain analyses of the Lothian Birth Cohort 1936: extending lifetime cognitive and brain phenotyping to the level of the synapse. Acta Neuropathol Commun 2015; 3:53. [PMID: 26335101 PMCID: PMC4559320 DOI: 10.1186/s40478-015-0232-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 08/19/2015] [Indexed: 12/14/2022] Open
Abstract
INTRODUCTION Non-pathological, age-related cognitive decline varies markedly between individuals andplaces significant financial and emotional strain on people, their families and society as a whole.Understanding the differential age-related decline in brain function is critical not only for the development oftherapeutics to prolong cognitive health into old age, but also to gain insight into pathological ageing suchas Alzheimer's disease. The Lothian Birth Cohort of 1936 (LBC1936) comprises a rare group of people forwhom there are childhood cognitive test scores and longitudinal cognitive data during older age, detailedstructural brain MRI, genome-wide genotyping, and a multitude of other biological, psycho-social, andepidemiological data. Synaptic integrity is a strong indicator of cognitive health in the human brain;however, until recently, it was prohibitively difficult to perform detailed analyses of synaptic and axonalstructure in human tissue sections. We have adapted a novel method of tissue preparation at autopsy toallow the study of human synapses from the LBC1936 cohort in unprecedented morphological andmolecular detail, using the high-resolution imaging techniques of array tomography and electronmicroscopy. This allows us to analyze the brain at sub-micron resolution to assess density, proteincomposition and health of synapses. Here we present data from the first donated LBC1936 brain andcompare our findings to Alzheimer's diseased tissue to highlight the differences between healthy andpathological brain ageing. RESULTS Our data indicates that compared to an Alzheimer's disease patient, the cognitively normalLBC1936 participant had a remarkable degree of preservation of synaptic structures. However,morphological and molecular markers of degeneration in areas of the brain associated with cognition(prefrontal cortex, anterior cingulate cortex, and superior temporal gyrus) were observed. CONCLUSIONS Our novel post-mortem protocol facilitates high-resolution neuropathological analysis of the well-characterized LBC1936 cohort, extending phenotyping beyond cognition and in vivo imaging to nowinclude neuropathological changes, at the level of single synapses. This approach offers an unprecedentedopportunity to study synaptic and axonal integrity during ageing and how it contributes to differences in agerelatedcognitive change.
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Walden M, Edwards JM, Dziewulska AM, Bergmann R, Saalbach G, Kan SY, Miller OK, Weckener M, Jackson RJ, Shirran SL, Botting CH, Florence GJ, Rohde M, Banfield MJ, Schwarz-Linek U. An internal thioester in a pathogen surface protein mediates covalent host binding. eLife 2015; 4. [PMID: 26032562 PMCID: PMC4450167 DOI: 10.7554/elife.06638] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 05/01/2015] [Indexed: 01/19/2023] Open
Abstract
To cause disease and persist in a host, pathogenic and commensal microbes must adhere to tissues. Colonization and infection depend on specific molecular interactions at the host-microbe interface that involve microbial surface proteins, or adhesins. To date, adhesins are only known to bind to host receptors non-covalently. Here we show that the streptococcal surface protein SfbI mediates covalent interaction with the host protein fibrinogen using an unusual internal thioester bond as a ‘chemical harpoon’. This cross-linking reaction allows bacterial attachment to fibrin and SfbI binding to human cells in a model of inflammation. Thioester-containing domains are unexpectedly prevalent in Gram-positive bacteria, including many clinically relevant pathogens. Our findings support bacterial-encoded covalent binding as a new molecular principle in host-microbe interactions. This represents an as yet unexploited target to treat bacterial infection and may also offer novel opportunities for engineering beneficial interactions. DOI:http://dx.doi.org/10.7554/eLife.06638.001 The human body is home to many trillions of microbes; most are harmless, but some may cause disease. To live inside a host, microbes must first attach to host tissues. This process involves multiple proteins on each microbe's surface, called adhesins, which interact with the molecules that make up these tissues. Like all proteins, adhesins are long chains of simpler building blocks called amino acids, and each amino acid is connected to the next via a strong ‘covalent’ bond. Adhesins, however, typically attach bacteria to host molecules through the combined strength of many weak ‘non-covalent’ interactions. It was recently discovered that one adhesin from a bacterium called Streptococcus pyogenes contains a rare, extra covalent bond—called a thioester—in an unusual location between two of its amino acids. S. pyogenes is a common cause of throat infections in humans, and can also cause the life-threatening ‘flesh-eating disease’. Walden, Edwards et al. have now used a range of computational, biochemical, structural biology and cell-based techniques to study other adhesins that have thioester bonds in more detail. Computational searches identified hundreds of bacterial proteins containing similar bonds. These included many from bacteria that infect humans: such as Streptococcus pneumoniae, which is the most common cause of pneumonia in adults; and Clostridium difficile, which is notorious for causing severe gut infections in hospital patients. Closer examination of the three-dimensional structures of three of these proteins—including one called SfbI from S. pyogenes—revealed that each had a clear thioester bond. Biochemical tests of an additional nine of the identified proteins strongly suggested they too contained thioester bonds. Walden, Edwards et al. then showed that SfbI was able to not only attach to tissues like conventional adhesins, but also chemically react with fibrinogen: a human protein that is essential for blood clotting and commonly found in inflamed tissues and healing wounds. This chemical reaction results in the formation of a covalent bond between SfbI and fibrinogen, which is as stable as the bonds that link the amino acids in a protein chain. Further experiments revealed that SfbI strongly binds to human cells grown in the lab under conditions that mimic tissue inflammation. Finally, Walden, Edwards et al. made a mutant version of SfbI that did not contain a thioester, and found that it could not interact with fibrinogen nor bind to human cells. Together, these findings suggest that thioesters in bacterial adhesins act like ‘chemical harpoons’, which microbes can use to irreversibly attach themselves to molecules within their host's tissues. This attachment mechanism has not been seen before in host-microbe interactions, and further research is now needed to explore whether interfering with this process could represent a new way to treat bacterial infections. DOI:http://dx.doi.org/10.7554/eLife.06638.002
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Odibo IN, Linam LE, Richter GE, Jackson RJ, Dajani NK. Extensive Fetal Congenital Subcutaneous Mixed Venous Lymphatic Lesion: Prenatal Diagnosis and Postnatal Management. AJP Rep 2015; 5. [PMID: 26199796 PMCID: PMC4502633 DOI: 10.1055/s-0034-1544107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vascular lesions may be categorized as proliferative tumors, such as hemangiomas, or nonproliferative malformations that include capillary, lymphatic, venous, arterial, or mixed lesions. Lymphatic malformations are benign localized congenital malformations of the lymphatic system. They may be microcystic or macrocystic lesions or a combination of both. The lesions may also be uniseptate or multiseptate, and are more commonly located in the head and neck or axillary region. Prenatal diagnosis is based on ultrasound and magnetic resonance imaging. Postnatal management largely depends on the size and location of the lesion. This is the first case report of prenatally diagnosed extensive subcutaneous macrocystic venous lymphatic malformation involving the fetal thorax, back, pelvis, and lower extremities. Prenatal course and postnatal management are described. This report will aid other specialists in the field of prenatal diagnosis and postnatal surgery in the evaluation and management of these patients.
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Xi Y, Day SL, Jackson RJ, Ranasinghe C. Role of novel type I interferon epsilon in mucosal immunity. Retrovirology 2012. [PMCID: PMC3441604 DOI: 10.1186/1742-4690-9-s2-p192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Jackson RJ, Gould TH, Thomas MJ. Worst Oxygenation Index during the first 24 hours of ventilation predicts mortality. Crit Care 2012. [PMCID: PMC3363508 DOI: 10.1186/cc10697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
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Baird WO, McGrother C, Abrams KR, Dugmore C, Jackson RJ. Access to dental services for people with a physical disability: a survey of general dental practitioners in Leicestershire, UK. COMMUNITY DENTAL HEALTH 2008; 25:248-252. [PMID: 19149304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
OBJECTIVE To investigate the availability of facilities, including parking, accessibility and toilet amenities, for physically disabled people at dental practices in Leicestershire, and views relating to the provision of treatment, as reported by general dental practitioners. BASIC RESEARCH DESIGN A cross-sectional postal questionnaire-based study. SETTING General Dental Service practices in Leicestershire, United Kingdom. PARTICIPANTS Questionnaires were sent to all General Dental Service practices (n=123) within Leicestershire. MAIN OUTCOME MEASURES Facilities for physically disabled people as reported by general dental practitioners and views of practitioners in relation to provision of treatment. RESULTS The response rate from general dental practices was 80%. The views of 120 (42%) of the 284 dentists approached relating to the provision of treatment to people with a physical disability were recorded. Although up to 77% of the dental practices were considered by practitioners to be accessible to someone using a wheelchair, only 7% also had suitable parking and toilet facilities. The majority of responding dentists treated patients with a physical disability, but 76% of practitioners found it difficult to provide treatment to this group. Concerns regarding the financial cost of providing treatment were raised. There is evidence that conditions are less than optimal in general practice settings for patients with a physical disability receiving treatment. Only nine of the 123 practices in Leicestershire had appropriate parking, access and toilet facilities for physically disabled people. CONCLUSION(S) Facilities for physically disabled people at general practices in Leicestershire are limited. If inequalities in dental health among the physically disabled are to be successfully reduced, steps must be taken to make practices more easily accessible with suitable facilities, and to increase awareness of services offered by appropriate dental practices.
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Hale-Donze H, Wahl SM, Jackson RJ, McGhee JR. Measurement of TGF-beta in biological fluids. ACTA ACUST UNITED AC 2008; Chapter 6:Unit 6.11. [PMID: 18432803 DOI: 10.1002/0471142735.im0611s41] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Transforming growth factor (TGF-beta) is an immunoregulatory cytokine produced by many different cell types, including lymphocytes and monocytes-macrophages. Two assays are described for the quantitation of TGF-beta activity in supernatant fluids. The bioassay for TGF-beta is based on the potent ability of TGF-beta to suppress lymphocyte proliferation. The radioreceptor assay is based on the ability of TGF-beta-containing supernatant fluids to inhibit the binding of radiolabeled TGF-beta to its cellular receptor. Two support protocols describe acid-activation and neutralization of TGF-beta.
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Baird WO, Jackson RJ, Worthington LS, Robinson PG. Perspectives of dentists in primary care ahead of the 'new ways of working'. Br Dent J 2007; 202:E24; discussion 614-5. [PMID: 17384587 DOI: 10.1038/bdj.2007.270] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2006] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To determine the future intentions and motivations of general dental practitioners (GDPs) relating to NHS dental practice in South Yorkshire. DESIGN Focus group discussions. SETTING General dental practices providing NHS care within South Yorkshire, United Kingdom. SUBJECTS (MATERIALS) AND METHODS Twenty-nine dental practitioners were purposively sampled and invited to take part in a series of focus groups. Focus groups were transcribed and data analysed to identify themes and concepts. MAIN OUTCOME MEASURES Themes and concepts relating to the current and future provision of dentistry and the proposed 'new ways of working' of the new dental contract. RESULTS The data fell into three broad categories: the organisational structures of dentistry; the future of dentistry; and the CDS. This paper focuses largely on the second category, the future of NHS dentistry. The first category related to the organisational structures of dentistry, and encompassed perceptions that dentistry was not a high priority for the Government and that current changes were politically motivated and to be implemented by PCTs with a lack of capacity for the management of such wide-reaching changes. The second category covered the future of NHS dentistry. For some, NHS dentistry was in a precarious and uncertain position, coupled with a lack of clarity and information on the 'new ways of working' and exacerbated by problems in the recruitment and retention of future dental practitioners. The last category dealt with views in connection with the CDS. CONCLUSION(S) In this 'snapshot in time' there was considerable uncertainty and instability within the general dental service against a backdrop of major organisational change. There was a need for information, guidance, openness and communication between the Government, PCTs and GDPs surrounding the implementation of the new contract.
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