Influence of cement type, excess removal, and polishing on the cement joint.

OBJECTIVES: To compare marginal gap width and depth with different cementation systems, excess removal, and after polishing. METHOD AND MATERIALS: In total, 80 composite crowns were milled, divided into ten groups, and cemented on identical artificial teeth. Eight crowns per group were fixed with (i) zinc phosphate cement (ZnOPh), (ii) glass-ionomer cement (GIC), (iii) resin-reinforced glass-ionomer cement (GIC mod), (iv) dual-curing adhesive composite (Comp dual), or (v) dual-curing self-adhesive composite (Comp SE dual). Excess removal was performed with a scaler after brief light-cure (tack-cure), final light-cure, during rubber or gel phase or by wiping with foam pellet. Curing was completed in chemical, dark cure, or light-curing modus. The specimens were polished and stored in water (37°C). The margins were digitized using a 3D laser-scanning microscope (VK-X100 series, Keyence). The width and the depth of the marginal gap were measured at 10 points between the crown margin and the preparation margin. RESULTS: The width after excess removal varied between 65.1 ± 15.7 µm (Comp dual, wipe, with polishing) and 208.6 ± 266.7 µm (Comp SE dual, dark cure, without polishing). The depth varied between 29.8 ± 22.2 µm (Comp dual, wipe, with polishing) and 89.5 ± 45.2 µm (Comp SE dual, dark cure, without polishing). The impact on gap width and depth was detected for fixation material, excess removal, and polishing. CONCLUSION: The gap depth and width depend on the luting material and the mode of access removal. Polishing can improve the gap quality, especially for GIC and resin-based systems.

Influence of fabrication settings on the in-vitro performance of subtractively manufactured resin-based molar crowns.

PURPOSE: To investigate the influence of milling parameters on the durability during in-vitro aging-simulation, and fracture force of resin-based composite crowns. MATERIALS AND METHODS: Identical molar crowns (n=8 per group) were milled from resin-based composite crowns (Grandio, VOCO, Germany) with different processing speed (soft, normal, fast) or level of details (very high, high, low) form 98mm discs. To investigate the influence of cooling, one group was milled wet. The influence of polishing was tested in two groups. All crowns were adhesively bonded on standardized resin-based composite molars. Aging was performed with thermal cycling and mechanical loading (2x3000x5°C/55°C, 2min, H20 dist., 1.2x106 force 50N). Fracture forces were determined (v=1mm/min, Z010, Zwick, Germany). STATISTICS: Pearson-correlation, one-way ANOVA, Bonferroni post-hoc-tests (α=0.05). RESULTS: All crowns survived TCML without any failures. The fracture values varied between 1237.3 ± 326.7N and 3308.6 ± 655.8N. Significant (p<0.001) differences between the individual manufacturing approaches were detected. Failure was categorized as a fracture of the crown and partial loosening of the crown. No different failure pattern was observed between the tested systems. CONCLUSION: A medium level of detail seems to be ideal to achieve highest fracture forces. No relationship existed between machining speed and fracture force. Fracture force was not affected by wet grinding. In individual cases, polishing reduced crown fracture values, due to reduced wall thickness.

T1 mapping of the prostate using Single-Shot T1FLASH and MOLLI MRI Techniques: Comparison of artifact burden and image quality.

PURPOSE: To assess artifact burden and image quality of different MRI T1 mapping techniques of the prostate. METHODS: Participants with suspected prostate cancer (PCa) were prospectively enrolled from June-October 2022 and examined with multiparametric prostate MRI (mpMRI; 3 T scanner; T1wi, T2wi, DWI und DCE). T1 mapping was performed before and after administration of gadolinium-based contrast-agent (GBCA) using (i) a modified Look-Locker inversion (MOLLI) technique and (ii) a novel single-shot T1FLASH inversion recovery technique. T2wi, DWI, T1FLASH and MOLLI sequences were systematically examined regarding prevalence of artifacts and image quality using a 5-point Likert-Scale. RESULTS: A total of n = 100 patients were included (median age: 68 years). T1FLASH maps (pre-and post-GBCA) showed metal artifacts in 7% of cases and susceptibility artifacts in 1%. For MOLLI maps, pre-GBCA metal and susceptibility artifacts were documented in 6.5% of cases each. MOLLI maps post-GBCA showed artifacts in 59% of cases resulting primarily from urinary GBCA excretion and GBCA accumulation at the bladder base (p < 0.01 versus T1FLASH post-GBCA). Image quality for T1FLASH pre-GBCA was rated at a mean 4.9+/-0.4 and for MOLLI at 4.8+/-0.6 (p = 0.14). Post-GBCA image quality was rated at a mean 4.9+/-0.4 for T1FLASH and at 3.7+/-1.1 for MOLLI (p < 0.001). CONCLUSIONS: T1FLASH maps provide a fast and robust method for quantification of T1 relaxation times of the prostate. T1FLASH is suitable for T1 mapping of the prostate following administration of contrast agents, while MOLLI T1 mapping is impaired through GBCA accumulation at the bladder base leading to severe image artifacts and reduced image quality.

Long-term Outcome After Acute Peripheral Facial Palsy.

PURPOSE: To analyze long-term outcomes in a large cohort of patients with acute peripheral facial palsy (APFP). METHODS: Hospital-based, cross-sectional study. Data were abstracted from the electronic medical record. Time to recovery was assessed with Kaplan-Meier survival analyses. Binary logistic regression analysis was used to identify factors associated with outcome. RESULTS: Three hundred seventy-two patients with APFP seen at a tertiary hospital between February 2015 and March 2021 were analyzed. Seasonal variation of APFP peaked in the early fall (September 29) and had a peak-to-low ratio of 1.36 (R 2 = 0.329, p < 0.001). Patients who tested positive for Lyme disease (10%) had an earlier peak (July 16) compared with those who were negative (October 15). Eighty-seven percent of patients had complete recovery (averaging 64 ± 61 days). Patients, with higher House-Brackmann (H-B) grades at presentation took longer to recover, were more likely to have aberrant regeneration and had lower final rates of recovery compared with those with lower H-B grades (χ 2 = 12.03, p < 0.001). Of the patients with residual palsies, 70% had evidence of aberrant regeneration, and nearly half of those had hemifacial spasm. CONCLUSIONS: Most patients with APFP achieve complete recovery within 1 year, including those positive for Lyme. More severe palsy at presentation portends a worse outcome.

Number needed to treat analysis applied to pembrolizumab plus chemotherapy for first-line treatment of non-squamous non-small cell lung cancer.

AIMS: Considering that healthcare systems' financial resources are limited, we aimed to analyze the number needed to treat (NNT) and cost of preventing an event (COPE) related to drug use from Supplementary Health System (SSS) perspective. METHODS: Data from KEYNOTE-189 (NCT02578680) were considered, comparing pembrolizumab + chemotherapy to chemotherapy alone. A cost-per-responder model was developed considering the 24- and 12-month time horizons for overall survival (OS) and progression-free survival (PFS) endpoints, respectively. Restricted mean survival time (RMST) and restricted mean time-on-treatment (ToT) were determined for NNT and COPE calculation. Costs were reported in American dollars (USD) and reflect those related to drug use. The analysis was conducted for the total indicated population, and an exploratory assessment was carried out for subgroups with different programmed death-ligand 1 (PD-L1) expression levels. RESULTS: Considering PFS data, the overall population NNTRMST to prevent a progression event with pembrolizumab + chemotherapy versus chemotherapy was 2.63 (95%CI: 1.90-4.02) with an estimated COPE of 251,038 USD (95%CI: 181,359-383,717) in the 12-months follow-up. Regarding OS endpoint, overall NNTRMST and COPE were 3.18 (95%CI: 2.20-5.31) and 414,163 (95%CI: 286,528-691,573) USD respectively, in the 24 months follow-up. The PFS NNT was lower with higher levels of PD-L1 expression (1.71, 3.22 and 5.53 for PD-L1 ≥ 50%, PD-L1 1%-49%, and PD-L1 < 1% groups, respectively), while there was no such apparent relationship for OS (3.23, 4.37 and 2.80 for PD-L1 ≥ 50%, PD-L1 1%-49%, and PD-L1 < 1% groups, respectively). The 95%CIs overlapped for PFS and OS NNT across the PD-L1 subgroups. CONCLUSION: The magnitude of benefit of the pembrolizumab combination used for first-line non-small cell lung cancer (NSCLC) treatment to improve survival compared to chemotherapy alone was confirmed. The exploratory analysis from the SSS perspective suggests no differences among the PDL-1 subgroups in terms of clinical benefit or economic impact.

Pre-existing health conditions and severe COVID-19 outcomes: an umbrella review approach and meta-analysis of global evidence.

BACKGROUND: This study applies an umbrella review approach to summarise the global evidence on the risk of severe COVID-19 outcomes in patients with pre-existing health conditions. METHODS: Systematic reviews (SRs) were identified in PubMed, Embase/Medline and seven pre-print servers until December 11, 2020. Due to the absence of age-adjusted risk effects stratified by geographical regions, a re-analysis of the evidence was conducted. Primary studies were extracted from SRs and evaluated for inclusion in the re-analysis. Studies were included if they reported risk estimates (odds ratio (OR), hazard ratio (HR), relative risk (RR)) for hospitalisation, intensive care unit admission, intubation or death. Estimated associations were extracted from the primary studies for reported pre-existing conditions. Meta-analyses were performed stratified for each outcome by regions of the World Health Organization. The evidence certainty was assessed using GRADE. Registration number CRD42020215846. RESULTS: In total, 160 primary studies from 120 SRs contributed 464 estimates for 42 pre-existing conditions. Most studies were conducted in North America, European, and Western Pacific regions. Evidence from Africa, South/Latin America, and the Eastern Mediterranean region was scarce. No evidence was available from the South-East Asia region. Diabetes (HR range 1.2-2.0 (CI range 1.1-2.8)), obesity (OR range 1.5-1.75 (CI range 1.1-2.3)), heart failure (HR range 1.3-3.3 (CI range 0.9-8.2)), COPD (HR range 1.12-2.2 (CI range 1.1-3.2)) and dementia (HR range 1.4-7.7 (CI range 1.2-39.6)) were associated with fatal COVID-19 in different regions, although the estimates varied. Evidence from Europe and North America showed that liver cirrhosis (OR range 3.2-5.9 (CI range 0.9-27.7)) and active cancer (OR range 1.6-4.7 (CI range 0.5-14.9)) were also associated with increased risk of death. Association between HIV and undesirable COVID-19 outcomes showed regional heterogeneity, with an increased risk of death in Africa (HR 1.7 (CI 1.3-2.2)). GRADE certainty was moderate to high for most associations. CONCLUSION: Risk of undesirable COVID-19 health outcomes is consistently increased in certain patient subgroups across geographical regions, showing high variability in others. The results can be used to inform COVID-19 vaccine prioritisation or other intervention strategies.

Pembrolizumab plus axitinib and nivolumab plus ipilimumab as first-line treatments of advanced intermediate- or poor-risk renal-cell carcinoma: a number needed to treat analysis from the Brazilian private perspective.

BACKGROUND: Considering clinical benefits of new combination therapies for metastatic renal-cell carcinoma (mRCC), this study aims to calculate the number needed to treat (NTT) and the cost of preventing an event (COPE) for pembrolizumab plus axitinib (P + A), and nivolumab plus ipilimumab (N + I) as first-line treatments, from the Brazilian private perspective. METHODS: Overall survival (OS) and progression-free survival (PFS) data for intermediate- and poor-risk groups were obtained from KEYNOTE-426 and CHECKMATE-214 trials for P + A and N + I, respectively, versus sunitinib as mRCC first-line treatment. RESULTS: Considering a 12-month time horizon, 6 patients should be treated with P + A to prevent one death with sunitinib use, resulting in a COPE of 3,773,865 BRL. Using N + I, NNT for 12-month OS rate was 13 compared to sunitinib, with a COPE of 6,357,965 BRL. Regarding PFS data, NNT was also 6 when comparing P + A versus sunitinib, with an estimated COPE of 3,773,865 BRL. Estimated NNT was 20 comparing N + I and sunitinib, resulting in a COPE of 10,172,744 BRL. Cost differences between two treatment options, reached more than 6 million BRL for PFS, and 2 million BRL for OS. CONCLUSION: At the 12-month landmark, P + A suggests better economic scenario versus N + I as first-line mRCC treatment option for intermediate- and poor-risk groups, through an indirect comparison using sunitinib as a common comparator.

Anti-PrPC antibody rescues cognition and synapses in transgenic alzheimer mice.

Objective: Amyloid-beta oligomers (Aßo) trigger the development of Alzheimer's disease (AD) pathophysiology. Cellular prion protein (PrPC) initiates synaptic damage as a high affinity receptor for Aßo. Here, we evaluated the preclinical therapeutic efficacy of a fully human monoclonal antibody against PrPC. This AZ59 antibody selectively targets the Aßo binding site in the amino-terminal unstructured domain of PrPC to avoid any potential risk of direct toxicity. Methods: Potency of AZ59 was evaluated by binding to PrPC, blockade of Aßo interaction and interruption of Aßo signaling. AZ59 was administered to mice by weekly intraperitoneal dosing and brain antibody measured. APP/PS1 transgenic mice were treated with AZ59 and assessed by memory tests, by brain biochemistry and by histochemistry for Aß, gliosis and synaptic density. Results: AZ59 binds PrPC with 100 pmol/L affinity and blocks human brain Aßo binding to PrPC, as well as prevents synaptotoxic signaling. Weekly i.p. dosing of 20 mg/kg AZ59 in a murine form achieves trough brain antibody levels greater than 10 nmol/L. Aged symptomatic APP/PS1 transgenic mice treated with AZ59 for 5-7 weeks show a full rescue of behavioral and synaptic loss phenotypes. This recovery occurs without clearance of plaque pathology or elimination of gliosis. AZ59 treatment also normalizes synaptic signaling abnormalities in transgenic brain. These benefits are dose-dependent and persist for at least 1 month after the last dose. Interpretation: Preclinical data demonstrate that systemic AZ59 therapy rescues central synapses and memory function from transgenic Alzheimer's disease pathology, supporting a disease-modifying therapeutic potential.

Rescue of Transgenic Alzheimer's Pathophysiology by Polymeric Cellular Prion Protein Antagonists.

Cellular prion protein (PrPC) binds the scrapie conformation of PrP (PrPSc) and oligomeric ß-amyloid peptide (Aßo) to mediate transmissible spongiform encephalopathy (TSE) and Alzheimer's disease (AD), respectively. We conducted cellular and biochemical screens for compounds blocking PrPC interaction with Aßo. A polymeric degradant of an antibiotic targets Aßo binding sites on PrPC with low nanomolar affinity and prevents Aßo-induced pathophysiology. We then identified a range of negatively charged polymers with specific PrPC affinity in the low to sub-nanomolar range, from both biological (melanin) and synthetic (poly [4-styrenesulfonic acid-co-maleic acid], PSCMA) origin. Association of PSCMA with PrPC prevents Aßo/PrPC-hydrogel formation, blocks Aßo binding to neurons, and abrogates PrPSc production by ScN2a cells. We show that oral PSCMA yields effective brain concentrations and rescues APPswe/PS1ΔE9 transgenic mice from AD-related synapse loss and memory deficits. Thus, an orally active PrPC-directed polymeric agent provides a potential therapeutic approach to address neurodegeneration in AD and TSE.

Alzheimer's Disease Risk Factor Pyk2 Mediates Amyloid-ß-Induced Synaptic Dysfunction and Loss.

Dozens of genes have been implicated in late onset Alzheimer's disease (AD) risk, but none has a defined mechanism of action in neurons. Here, we show that the risk factor Pyk2 (PTK2B) localizes specifically to neurons in adult brain. Absence of Pyk2 has no major effect on synapse formation or the basal parameters of synaptic transmission in the hippocampal Schaffer collateral pathway. However, the induction of synaptic LTD is suppressed in Pyk2-null slices. In contrast, deletion of Pyk2 expression does not alter LTP under control conditions. Of relevance for AD pathophysiology, Pyk2-/- slices are protected from amyloid-ß-oligomer (Aßo)-induced suppression of LTP in hippocampal slices. Acutely, a Pyk2 kinase inhibitor also prevents Aßo-induced suppression of LTP in WT slices. Female and male transgenic AD model mice expressing APPswe/PSEN1ΔE9 require Pyk2 for age-dependent loss of synaptic markers and for impairment of learning and memory. However, absence of Pyk2 does not alter Aß accumulation or gliosis. Therefore, the Pyk2 risk gene is directly implicated in a neuronal Aßo signaling pathway impairing synaptic anatomy and function.SIGNIFICANCE STATEMENT Genetic variation at the Pyk2 (PTK2B) locus is a risk for late onset Alzheimer's disease (AD), but the pathophysiological role of Pyk2 is not clear. Here, we studied Pyk2 neuronal function in mice lacking expression with and without transgenes generating amyloid-ß (Aß) plaque pathology. Pyk2 is not required for basal synaptic transmission or LTP, but participates in LTD. Hippocampal slices lacking Pyk2 are protected from AD-related Aß oligomer suppression of synaptic plasticity. In transgenic AD model mice, deletion of Pyk2 rescues synaptic loss and learning/memory deficits. Therefore, Pyk2 plays a central role in AD-related synaptic dysfunction mediating Aß-triggered dysfunction.

Somatosensory profiles in acute herpes zoster and predictors of postherpetic neuralgia.

This prospective cohort study aimed to characterize the sensory profile during acute herpes zoster (AHZ) and to explore sensory signs as well as physical and psychosocial health as predictors for postherpetic neuralgia (PHN). Results of quantitative sensory testing of 74 patients with AHZ at the affected site and at the distant contralateral control site were compared to a healthy control group. Pain characteristics (Neuropathic Pain and Symptom Inventory and SES), physical functioning, and psychosocial health aspects (Pain Disability Index, SF-36, and STAI) were assessed by questionnaires. Patients with PHN (n = 13) at 6-month follow-up were compared to those without PHN (n = 45). Sensory signs at the affected site were thermal and vibratory hypesthesia, dynamic mechanical allodynia (DMA), pressure hyperalgesia, and high wind-up (18%-29%), as well as paradoxical heat sensations and pinprick hypalgesia (13.5%). The unaffected control site exhibited thermal and vibratory hypesthesia, DMA, and pressure hyperalgesia. Dynamic mechanical allodynia and pinprick hypalgesia were mutually exclusive. Postherpetic neuralgia was associated with DMA (38.5% vs 6.7%; P = 0.010) and vibratory hypesthesia (38.5% vs 11.1%; P = 0.036) at the control site, with mechanical gain and/or loss combined with normal thermal detection (affected site: 69.2% vs 31.1%; P = 0.023; control site: 53.8% vs 15.5%; P = 0.009). Pain Disability Index (P = 0.036) and SES affective pain perception scores (P = 0.031) were over 50% higher, and 6 of 8 SF-36 subscores were over 50% lower (P < 0.045) in PHN. Sensory profiles in AHZ indicate deafferentation and central but not peripheral sensitization. Sensory signs at distant body sites, strong affective pain perception, as well as reduced quality of life and physical functioning in the acute phase may reflect risk factors for the transition to PHN.

The NMDA receptor antagonist Radiprodil reverses the synaptotoxic effects of different amyloid-beta (Aß) species on long-term potentiation (LTP).

Aß1-42 is well accepted to be a primary early pathogenic agent in Alzheimer's disease (AD). However, other amyloid peptides are now gaining considerable attention as potential key participants in AD due to their proposed higher neuronal toxicity. Impairment of the glutamatergic system is also widely accepted to be associated with pathomechanisms underlying AD. There is ample evidence that Aß1-42 affects GLUN2B subunit containing N-methyl-D-aspartate receptor function and abolishes the induction of long term potentiation (LTP). In this study we show that different ß-amyloid species, 1-42 Aß1-42 and 1-40 (Aß1-40) as well as post-translationally modified forms such as pyroglutamate-modified amyloid-(AßpE3) and nitrated Aß (3NTyr10-Aß), when applied for 90 min to murine hippocampal slices, concentration-dependently prevented the development of CA1-LTP after tetanic stimulation of the Schaffer collaterals with IC50s of 2, 9, 2 and 35 nM, respectively whilst having no effect on baseline AMPA receptor mediated fEPSPs. Aß1-43 had no effect. Interestingly, the combination of all Aß species did not result in any synergistic or additive inhibitory effect on LTP - the calculated pooled Aß species IC50 was 20 nM. A low concentration (10 nM) of the GLUN2B receptor antagonist Radiprodil restored LTP in the presence of Aß1-42, 3NTyr10-Aß, Aß1-40, but not AßpE3. In contrast to AMPA receptor mediated fEPSPs, all different ß-amyloid species tested at 50 nM supressed baseline NMDA-EPSC amplitudes. Similarly, all different Aß species tested decreased spine density. As with LTP, Radiprodil (10 nM) reversed the synaptic toxicity of Aß species but not that of AßpE3. These data do not support the enhanced toxic actions reported for some Aß species such as AßpE3, nor synergistic toxicity of the combination of different Aß species. However, whilst in our hands AßpE3-42 was actually less toxic than Aß1-42, its effects were not reversed by Radiprodil indicating that the target receptors/subunits mediating such synaptotoxicity may differ between the different Aß species tested.

Conditional Deletion of Prnp Rescues Behavioral and Synaptic Deficits after Disease Onset in Transgenic Alzheimer's Disease.

Biochemical and genetic evidence implicate soluble oligomeric amyloid-ß (Aßo) in triggering Alzheimer's disease (AD) pathophysiology. Moreover, constitutive deletion of the Aßo-binding cellular prion protein (PrPC) prevents development of memory deficits in APPswe/PS1ΔE9 mice, a model of familial AD. Here, we define the role of PrPC to rescue or halt established AD endophenotypes in a therapeutic disease-modifying time window after symptom onset. Deletion of Prnp at either 12 or 16 months of age fully reverses hippocampal synapse loss and completely rescues preexisting behavioral deficits by 17 months. In contrast, but consistent with a neuronal function for Aßo/PrPC signaling, plaque density, microgliosis, and astrocytosis are not altered. Degeneration of catecholaminergic neurons remains unchanged by PrPC reduction after disease onset. These results define the potential of targeting PrPC as a disease-modifying therapy for certain AD-related phenotypes after disease onset.SIGNIFICANCE STATEMENT The study presented here further elucidates our understanding of the soluble oligomeric amyloid-ß-Aßo-binding cellular prion protein (PrPC) signaling pathway in a familial form of Alzheimer's disease (AD) by implicating PrPC as a potential therapeutic target for AD. In particular, genetic deletion of Prnp rescued several familial AD (FAD)-associated phenotypes after disease onset in a mouse model of FAD. This study underscores the therapeutic potential of PrPC deletion given that patients already present symptoms at the time of diagnosis.

Silent Allosteric Modulation of mGluR5 Maintains Glutamate Signaling while Rescuing Alzheimer's Mouse Phenotypes.

Metabotropic glutamate receptor 5 (mGluR5) has been implicated in Alzheimer's disease (AD) pathology. We sought to understand whether mGluR5's role in AD requires glutamate signaling. We used a potent mGluR5 silent allosteric modulator (SAM, BMS-984923) to separate its well-known physiological role in glutamate signaling from a pathological role in mediating amyloid-ß oligomer (Aßo) action. Binding of the SAM to mGluR5 does not change glutamate signaling but strongly reduces mGluR5 interaction with cellular prion protein (PrPC) bound to Aßo. The SAM compound prevents Aßo-induced signal transduction in brain slices and in an AD transgenic mouse model, the APPswe/PS1ΔE9 strain. Critically, 4 weeks of SAM treatment rescues memory deficits and synaptic depletion in the APPswe/PS1ΔE9 transgenic mouse brain. Our data show that mGluR5's role in Aßo-dependent AD phenotypes is separate from its role in glutamate signaling and silent allosteric modulation of mGluR5 has promise as a disease-modifying AD intervention with a broad therapeutic window.

Early Activation of Experience-Independent Dendritic Spine Turnover in a Mouse Model of Alzheimer's Disease.

Synaptic loss is critical in Alzheimer's disease (AD), but the dynamics of synapse turnover are poorly defined. We imaged dendritic spines in transgenic APPswe/PSen1∆E9 (APP/PS1) cerebral cortex. Dendritic spine turnover is increased far from plaque in aged APP/PS1 mice, and in young APP/PS1 mice prior to plaque formation. Dysregulation occurs in the presence of soluble Aß oligomer and requires cellular prion protein (PrPC). APP/PS1 mice lack responsiveness of spine turnover to sensory stimulation. Critically, enhanced spine turnover is coupled with the loss of persistent spines starting early and continuing with age. To evaluate mechanisms of experience-independent supranormal spine turnover, we analyzed the transcriptome of young APP/PS1 mouse brain when turnover is altered but synapse density and memory are normal, and plaque and inflammation are absent. Early PrPC-dependent expression changes occur in synaptic and lipid-metabolizing genes. Thus, pathologic synaptic dysregulation underlying AD begins at a young age prior to Aß plaque.

Oligomers of Amyloid ß Prevent Physiological Activation of the Cellular Prion Protein-Metabotropic Glutamate Receptor 5 Complex by Glutamate in Alzheimer Disease.

The dysfunction and loss of synapses in Alzheimer disease are central to dementia symptoms. We have recently demonstrated that pathological Amyloid ß oligomer (Aßo) regulates the association between intracellular protein mediators and the synaptic receptor complex composed of cellular prion protein (PrP(C)) and metabotropic glutamate receptor 5 (mGluR5). Here we sought to determine whether Aßo alters the physiological signaling of the PrP(C)-mGluR5 complex upon glutamate activation. We provide evidence that acute exposure to Aßo as well as chronic expression of familial Alzheimer disease mutant transgenes in model mice prevents protein-protein interaction changes of the complex induced by the glutamate analog 3,5-dihydroxyphenylglycine. We further show that 3,5-dihydroxyphenylglycine triggers the phosphorylation and activation of protein-tyrosine kinase 2-ß (PTK2B, also referred to as Pyk2) and of calcium/calmodulin-dependent protein kinase II in wild-type brain slices but not in Alzheimer disease transgenic brain slices or wild-type slices incubated with Aßo. This study further distinguishes two separate Aßo-dependent signaling cascades, one dependent on extracellular Ca(2+) and Fyn kinase activation and the other dependent on the release of Ca(2+) from intracellular stores. Thus, Aßo triggers multiple distinct PrP(C)-mGluR5-dependent events implicated in neurodegeneration and dementia. We propose that targeting the PrP(C)-mGluR5 complex will reverse aberrant Aßo-triggered states of the complex to allow physiological fluctuations of glutamate signaling.

Metabotropic glutamate receptor 5 couples cellular prion protein to intracellular signalling in Alzheimer's disease.

Alzheimer's disease-related phenotypes in mice can be rescued by blockade of either cellular prion protein or metabotropic glutamate receptor 5. We sought genetic and biochemical evidence that these proteins function cooperatively as an obligate complex in the brain. We show that cellular prion protein associates via transmembrane metabotropic glutamate receptor 5 with the intracellular protein mediators Homer1b/c, calcium/calmodulin-dependent protein kinase II, and the Alzheimer's disease risk gene product protein tyrosine kinase 2 beta. Coupling of cellular prion protein to these intracellular proteins is modified by soluble amyloid-ß oligomers, by mouse brain Alzheimer's disease transgenes or by human Alzheimer's disease pathology. Amyloid-ß oligomer-triggered phosphorylation of intracellular protein mediators and impairment of synaptic plasticity in vitro requires Prnp-Grm5 genetic interaction, being absent in transheterozygous loss-of-function, but present in either single heterozygote. Importantly, genetic coupling between Prnp and Grm5 is also responsible for signalling, for survival and for synapse loss in Alzheimer's disease transgenic model mice. Thus, the interaction between metabotropic glutamate receptor 5 and cellular prion protein has a central role in Alzheimer's disease pathogenesis, and the complex is a potential target for disease-modifying intervention.

Prion-Protein-interacting Amyloid-ß Oligomers of High Molecular Weight Are Tightly Correlated with Memory Impairment in Multiple Alzheimer Mouse Models.

Alzheimer disease (AD) is characterized by amyloid-ß accumulation, with soluble oligomers (Aßo) being the most synaptotoxic. However, the multivalent and unstable nature of Aßo limits molecular characterization and hinders research reproducibility. Here, we characterized multiple Aßo forms throughout the life span of various AD mice and in post-mortem human brain. Aßo exists in several populations, where prion protein (PrP(C))-interacting Aßo is a high molecular weight Aß assembly present in multiple mice and humans with AD. Levels of PrP(C)-interacting Aßo match closely with mouse memory and are equal or superior to other Aß measures in predicting behavioral impairment. However, Aßo metrics vary considerably between mouse strains. Deleting PrP(C) expression in mice with relatively low PrP(C)-interacting Aßo (Tg2576) results in partial rescue of cognitive performance as opposed to complete recovery in animals with a high percentage of PrP(C)-interacting Aßo (APP/PSEN1). These findings highlight the relative contributions and interplay of Aßo forms in AD.

Fyn inhibition rescues established memory and synapse loss in Alzheimer mice.

OBJECTIVE: Currently no effective disease-modifying agents exist for the treatment of Alzheimer disease (AD). The Fyn tyrosine kinase is implicated in AD pathology triggered by amyloid-ß oligomers (Aßo) and propagated by Tau. Thus, Fyn inhibition may prevent or delay disease progression. Here, we sought to repurpose the Src family kinase inhibitor oncology compound, AZD0530, for AD. METHODS: The pharmacokinetics and distribution of AZD0530 were evaluated in mice. Inhibition of Aßo signaling to Fyn, Pyk2, and Glu receptors by AZD0530 was tested by brain slice assays. After AZD0530 or vehicle treatment of wild-type and AD transgenic mice, memory was assessed by Morris water maze and novel object recognition. For these cohorts, amyloid precursor protein (APP) metabolism, synaptic markers (SV2 and PSD-95), and targets of Fyn (Pyk2 and Tau) were studied by immunohistochemistry and by immunoblotting. RESULTS: AZD0530 potently inhibits Fyn and prevents both Aßo-induced Fyn signaling and downstream phosphorylation of the AD risk gene product Pyk2, and of NR2B Glu receptors in brain slices. After 4 weeks of treatment, AZD0530 dosing of APP/PS1 transgenic mice fully rescues spatial memory deficits and synaptic depletion, without altering APP or Aß metabolism. AZD0530 treatment also reduces microglial activation in APP/PS1 mice, and rescues Tau phosphorylation and deposition abnormalities in APP/PS1/Tau transgenic mice. There is no evidence of AZD0530 chronic toxicity. INTERPRETATION: Targeting Fyn can reverse memory deficits found in AD mouse models, and rescue synapse density loss characteristic of the disease. Thus, AZD0530 is a promising candidate to test as a potential therapy for AD.