Psychosis in Alzheimer Disease and Elevations in Disease-Relevant Biomarkers.

Importance: The emergence of psychotic symptoms in Alzheimer disease (AD) is associated with accelerated cognitive and functional decline that may be related to disease pathology. Objective: To investigate the longitudinal dynamics of plasma tau phosphorylated at threonine 181 (p-tau181) and neurofilament light chain protein (NfL) levels in association with the emergence of psychotic symptoms (delusions and hallucinations) in the context of AD. Design, Setting, and Participants: This cohort study used longitudinal data from the Alzheimer Disease Neuroimaging Initiative (ADNI). Baseline analyses compared patients with mild cognitive impairment (MCI) and AD (both with psychosis [AD+P] and without psychosis [AD-P]) and participants who were cognitively unimpaired (CU). For the longitudinal analysis, participants with MCI and AD were subdivided into patients with evidence of psychosis at baseline (AD+P baseline) and patients free of psychosis at baseline who showed incidence of psychosis over the course of the study (AD+P incident). Study data were analyzed between June and November 2023. Exposures: Plasma p-tau181 and NfL measures in individuals with MCI and AD, both with and without psychosis. Main Outcomes and Measures: Plasma p-tau181 and NfL quantifications up to 48 months and concurrent assessments of presence or absence of delusions and hallucinations via the Neuropsychiatric Inventory (NPI) questionnaire. Results: The cohort included 752 participants with AD (mean [SD] age, 74.2 [7.7] years; 434 male [57.7%]). A total of 424 CU participants had a mean (SD) age of 75.4 (6.6) years of whom 222 were female (52.4%). In the longitudinal analysis of p-tau181 trajectories of the AD+P group, the group of patients who showed incidence of psychosis over the course of follow-up (AD+P incident) demonstrated an associated increase in plasma p-tau181 levels compared with the group of patients who had psychosis at baseline (AD+P baseline) and showed an associated decrease in plasma p-tau181 levels (F4, 117 = 3.24; P = .01). The mean slope of p-tau181 change was significantly different in AD+P incident and AD+P baseline groups (F5,746 = 86.76, P < .0001) and when only individuals with amyloid-ß positivity (Aß+), which was determined using positron emission tomography, were compared (F5,455 = 84.60, P < .001). Patients who experienced psychosis at any time had increased levels of NfL relative to those who never experienced psychosis. Conclusions and Relevance: Results of this cohort study suggest that the emergence of psychosis in AD was associated with elevations in plasma levels of p-tau181, highlighting the potential utility of plasma p-tau181 as a biomarker of neuropsychiatric illness in AD, which could have implications for predictive and treatment response strategies.

Association between pre-dementia psychiatric diagnoses and all-cause dementia is independent from polygenic dementia risks in the UK Biobank.

BACKGROUND: Psychiatric disorders have been associated with higher risk for future dementia. Understanding how pre-dementia psychiatric disorders (PDPD) relate to established dementia genetic risks has implications for dementia prevention. METHODS: In this retrospective cohort study, we investigated the relationships between polygenic risk scores for Alzheimer's disease (AD PRS), PDPD, alcohol use disorder (AUD), and subsequent dementia in the UK Biobank (UKB) and tested whether the relationships are consistent with different causal models. FINDINGS: Among 502,408 participants, 9352 had dementia. As expected, AD PRS was associated with greater risk for dementia (odds ratio (OR) 1.62, 95% confidence interval (CI), 1.59-1.65). A total of 94,237 participants had PDPD, of whom 2.6% (n = 2519) developed subsequent dementia, compared to 1.7% (n = 6833) of 407,871 participants without PDPD. Accordingly, PDPD were associated with 73% greater risk of incident dementia (OR 1.73, 1.65-1.83). Among dementia subtypes, the risk increase was 1.5-fold for AD (n = 3365) (OR 1.46, 1.34-1.59) and 2-fold for vascular dementia (VaD, n = 1823) (OR 2.08, 1.87-2.32). Our data indicated that PDPD were neither a dementia prodrome nor a mediator for AD PRS. Shared factors for both PDPD and dementia likely substantially account for the observed association, while a causal role of PDPD in dementia could not be excluded. AUD could be one of the shared causes for PDPD and dementia. INTERPRETATION: Psychiatric diagnoses were associated with subsequent dementia in UKB participants, and the association is orthogonal to established dementia genetic risks. Investigating shared causes for psychiatric disorders and dementia would shed light on this dementia pathway. FUNDING: US NIH (K08AG054727).

The Impact of Muscarinic Antagonism on Psychosis-Relevant Behaviors and Striatal [11C] Raclopride Binding in Tau Mouse Models of Alzheimer's Disease.

Psychosis that occurs over the course of Alzheimer's disease (AD) is associated with increased caregiver burden and a more rapid cognitive and functional decline. To find new treatment targets, studies modeling psychotic conditions traditionally employ agents known to induce psychosis, utilizing outcomes with cross-species relevance, such as locomotive activity and sensorimotor gating, in rodents. In AD, increased burdens of tau pathology (a diagnostic hallmark of the disease) and treatment with anticholinergic medications have, separately, been reported to increase the risk of psychosis. Recent evidence suggests that muscarinic antagonists may increase extracellular tau. Preclinical studies in AD models have not previously utilized muscarinic cholinergic antagonists as psychotomimetic agents. In this report, we utilize a human-mutant-tau model (P301L/COMTKO) and an over-expressed non-mutant human tau model (htau) in order to compare the impact of antimuscarinic (scopolamine 10 mg/kg/day) treatment with dopaminergic (reboxetine 20 mg/kg/day) treatment, for 7 days, on locomotion and sensorimotor gating. Scopolamine increased spontaneous locomotion, while reboxetine reduced it; neither treatment impacted sensorimotor gating. In the P301L/COMTKO, scopolamine treatment was associated with decreased muscarinic M4 receptor expression, as quantified with RNA-seq, as well as increased dopamine receptor D2 signaling, as estimated with Micro-PET [11C] raclopride binding. Scopolamine also increased soluble tau in the striatum, an effect that partially mediated the observed increases in locomotion. Studies of muscarinic agonists in preclinical tau models are warranted to determine the impact of treatment-on both tau and behavior-that may have relevance to AD and other tauopathies.

Anesthesia promotes acute expression of genes related to Alzheimer's disease and latent tau aggregation in transgenic mouse models of tauopathy.

BACKGROUND: Exposure to anesthesia in the elderly might increase the risk of dementia. Although the mechanism underlying the association is uncertain, anesthesia has been shown to induce acute tau hyperphosphorylation in preclinical models. We sought to investigate the impact of anesthesia on gene expression and on acute and long-term changes in tau biochemistry in transgenic models of tauopathy in order to better understand how anesthesia influences the pathophysiology of dementia. METHODS: We exposed mice with over-expressed human mutant tau (P301L and hyperdopaminergic COMTKO/P301L) to two hours of isoflurane and compared anesthetized mice to controls at several time points. We evaluated tau hyperphosphorylation with quantitative high-sensitivity enzyme-linked immunosorbent assay and performed differential expression and functional transcriptome analyses following bulk mRNA-sequencing. RESULTS: Anesthesia induced acute hyperphosphorylation of tau at epitopes related to Alzheimer's disease (AD) in both P301L-based models. Anesthesia was associated with differential expression of genes in the neurodegenerative pathways (e.g., AD-risk genes ApoE and Trem2) and thermogenesis pathway, which is related to both mammalian hibernation and tau phosphorylation. One and three months after anesthesia, hyperphosphorylated tau aggregates were increased in the anesthetized mice. CONCLUSIONS: Anesthesia may influence the expression of AD-risk genes and induce biochemical changes in tau that promote aggregation even after single exposure. Further preclinical and human studies are necessary to establish the relevance of our transcriptomic and biochemical findings in these preclinical models to the pathogenesis of dementia following anesthesia. TRIAL REGISTRATION: Not applicable.

Psychotropic Medication Use Is Associated With Greater 1-Year Incidence of Dementia After COVID-19 Hospitalization.

Background: COVID-19 has been associated with an increased risk of incident dementia (post-COVID dementia). Establishing additional risk markers may help identify at-risk individuals and guide clinical decision-making. Methods: We investigated pre-COVID psychotropic medication use (exposure) and 1-year incidence of dementia (outcome) in 1,755 patients (≥65 years) hospitalized with COVID-19. Logistic regression models were used to examine the association, adjusting for demographic and clinical variables. For further confirmation, we applied the Least Absolute Shrinkage and Selection Operator (LASSO) regression and a machine learning (Random Forest) algorithm. Results: One-year incidence rate of post-COVID dementia was 12.7% (N = 223). Pre-COVID psychotropic medications (OR = 2.7, 95% CI: 1.8-4.0, P < 0.001) and delirium (OR = 3.0, 95% CI: 1.9-4.6, P < 0.001) were significantly associated with greater 1-year incidence of post-COVID dementia. The association between psychotropic medications and incident dementia remained robust when the analysis was restricted to the 423 patients with at least one documented neurological or psychiatric diagnosis at the time of COVID-19 admission (OR = 3.09, 95% CI: 1.5-6.6, P = 0.002). Across different drug classes, antipsychotics (OR = 2.8, 95% CI: 1.7-4.4, P < 0.001) and mood stabilizers/anticonvulsants (OR = 2.4, 95% CI: 1.39-4.02, P = 0.001) displayed the greatest association with post-COVID dementia. The association of psychotropic medication with dementia was further confirmed with Random Forest and LASSO analysis. Conclusion: Confirming prior studies we observed a high dementia incidence in older patients after COVID-19 hospitalization. Pre-COVID psychotropic medications were associated with higher risk of incident dementia. Psychotropic medications may be risk markers that signify neuropsychiatric symptoms during prodromal dementia, and not mutually exclusive, contribute to post-COVID dementia.

The impact of pimavanserin on psychotic phenotypes and tau phosphorylation in the P301L/COMT- and rTg(P301L)4510 mouse models of Alzheimer's disease.

INTRODUCTION: Psychosis in Alzheimer's disease (AD) is associated with grave clinical consequences including a precipitous cognitive decline and a hastened demise. These outcomes are aggravated by use of existing antipsychotic medications, which are also associated with cognitive decline and increased mortality; preclinical models that would develop new therapeutic approaches are desperately needed. The current report evaluates the ability of the neoteric antipsychotic, pimavanserin, to normalize hyperkinesis and sensorimotor gating in the novel catechol-O-methyltransferase (COMT) deleted P301L/COMT- and rTg(P301L)4510 models of psychotic AD, and the impact of pimavanserin on tau pathology. METHODS: Female P301L/COMT- mice were behaviorally characterized for abnormalities of locomotion and sensorimotor gating, and biochemically characterized for patterns of tau phosphorylation relative to relevant controls utilizing high-sensitivity tau enzyme-linked immunosorbent assay (ELISA). Female P301L/COMT- and rTg(P301L)4510 mice were randomized to pimavanserin or vehicle treatment to study the ability of pimavanserin to normalize locomotion and rescue sensorimotor gating. Additionally, high-sensitivity tau ELISA was used to investigate the impact of treatment on tau phosphorylation. RESULTS: P301L/COMT- mice evidenced a hyperlocomotive phenotype and deficits of sensorimotor gating relative to wild-type mice on the same background, and increased tau phosphorylation relative to COMT-competent P301L mice. Pimavanserin normalized the hyperkinetic phenotype in both the P301L/COMT- and rTg(P301L)4510 mice but had no impact on sensorimotor gating in either model. Pimavanserin treatment had little impact on tau phosphorylation patterns. DISCUSSION: These data suggest that pimavanserin ameliorates tau-driven excessive locomotion. Given the morbidity associated with aberrant motor behaviors such as pacing in AD and lack of effective treatments, future studies of the impact of pimavanserin on actigraphy in patients with this syndrome may be warranted.

Greater effect of polygenic risk score for Alzheimer's disease among younger cases who are apolipoprotein E-ε4 carriers.

To evaluate how age and apolipoprotein E-ε4 (APOE4) status interact with APOE-independent polygenic risk score (PRSnon-APOE), we estimated PRSnon-APOE in superagers (age ≥ 90 years, N = 346), 89- controls (age 60-89, N = 2930), and Alzheimer's disease (AD) cases (N = 1760). Using superagers, we see a nearly 5 times greater odds ratio (OR) for AD comparing the top PRSnon-APOE decile to the lowest decile (OR = 4.82, p = 2.5 × 10-6), which is twice the OR as using 89- controls (OR = 2.38, p = 4.6 × 10-9). Thus PRSnon-APOE is correlated with age, which in turn is associated with APOE. Further exploring these relationships, we find that PRSnon-APOE modifies age at onset among APOE4 carriers, but not among noncarriers. More specifically, PRSnon-APOE in the top decile predicts an age at onset 5 years earlier compared with the lowest decile (70.1 vs. 75.0 years; t-test p = 2.4 × 10-5) among APOE4 carriers. This disproportionally large PRSnon-APOE among younger APOE4-positive cases is reflected in a significant statistical interaction between APOE4 status and age at onset (ß = -0.02, p = 4.8 × 10-3) as a predictor of PRSnon-APOE. Thus, the known AD risk variants are particularly detrimental in young APOE4 carriers.

Animal Models of Psychosis in Alzheimer Disease.

Psychosis in Alzheimer Disease (AD) represents a distinct clinicopathologic variant associated with increased cognitive and functional morbidity and an accelerated disease course. To date, extant treatments offer modest benefits with significant risks. The development of new pharmacologic treatments for psychosis in AD would be facilitated by validated preclinical models with which to test candidate interventions. The current review provides a brief summary of the process of validating animal models of human disease together with a critical analysis of the challenges posed in attempting to apply those standards to AD-related behavioral models. An overview of phenotypic analogues of human cognitive and behavioral impairments, with an emphasis on those relevant to psychosis, in AD-related mouse models is provided, followed by an update on recent progress in efforts to translate findings in the pathophysiology of psychotic AD into novel models. Finally, some future directions are suggested to expand the catalogue of psychosis-relevant phenotypes that may provide a sturdier framework for model development and targets for preclinical treatment outcomes.

Increased tau phosphorylation follows impeded dopamine clearance in a P301L and novel P301L/COMT-deleted (DM) tau mouse model.

In Alzheimer's disease, the phosphorylation of tau is a critical event preceding the formation of neurofibrillary tangles. Previous work exploring the impact of a dopamine blocking antipsychotic on tau phosphorylation in a tau transgenic model suggested that extracellular dopamine may play a regulatory role in the phosphorylation state of tau. In order to test this hypothesis, and in order to develop a mouse model of impaired dopamine metabolism and tauopathy, an extant P301L transgenic tau model of Alzheimer's disease and a novel P301L/catechol-O-methyltransferase deleted model (DM mouse) were treated with the norepinephrine reuptake inhibitor reboxetine, and prefrontal dopamine concentrations and the phosphorylated state of tau was quantified. In two experiments, male and female P301L+/+//COMT+/+ and P301L+/+//COMT-/- (DM) mice were treated with reboxetine 20 mg/kg IP. In one experiment, acutely following reboxetine injection, the prefrontal cortex of mice were microdialyzed for dopamine, and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, utilizing the MetaQuant technique. In another experiment, acutely following reboxetine injections, tau phosphorylation was quantified in the frontal cortex, striatum, and hippocampus of the mice. Reboxetine injections were followed by significant increases from baseline in extracellular dopamine concentrations in P301L and DM mice, with significantly higher peak levels in the DM mice. Treatment was also followed by increases in tau phosphorylation spread throughout brain regions, with a larger impact on female mice. Extracellular dopamine concentrations exert an influence on the phosphorylation state of tau, with surges in dopamine associating with acute increases in tau phosphorylation.

The Relational and Item-Specific Encoding Task in Mild Cognitive Impairment and Alzheimer Disease.

BACKGROUND: The Relational and Item-Specific Encoding task (RISE) measures episodic memory subcomponents, including item-specific and relational encoding of to-be-remembered stimuli. These memory components are neurobiologically relevant because they may engage distinct subregions of the medial temporal lobe, perirhinal and entorhinal cortices, parahippocampus, and hippocampus. METHODS: A total of 125 participants, including 84 healthy controls (HC), 22 mild cognitive impairment-diagnosed and 19 Alzheimer disease (AD)-diagnosed participants, were administered the RISE and neuropsychological measures. Stepwise linear regressions assessed prediction of functional ability from RISE d' measures. ANOVAs and logistic regressions determined the ability of the RISE to discriminate between the diagnostic groups. In addition, the psychometric properties of the RISE were examined. RESULTS: RISE measures predicted diagnosis with pseudo R2 values in the range of 0.25-0.30. Receiver operating characteristic curves demonstrated adequate sensitivity and specificity with areas under the curve in the range of 0.78-0.98. Memory following relational encoding was a significant predictor of everyday functional competence. The RISE had acceptable psychometric properties, with the exception of floor effects in the AD group. CONCLUSION: The RISE measures significantly predicted diagnosis and predicted everyday functional competence. The RISE offers unique advantages in the assessment of HC and individuals with preclinical AD.

Differential burden of rare protein truncating variants in Alzheimer's disease patients compared to centenarians.

We compared coding region variants of 53 cognitively healthy centenarians and 45 patients with Alzheimer's disease (AD), all of Ashkenazi Jewish (AJ) ancestry. Despite the small sample size, the known AD risk variant APOE4 reached genome-wide significance, indicating the advantage of utilizing 'super-controls'. We restricted our subsequent analysis to rare variants observed at most once in the 1000 Genomes database and having a minor allele frequency below 2% in our AJ sample. We compared the burden of predicted protein altering variants between cases and controls as normalized by the level of rare synonymous variants. We observed an increased burden among AD subjects for predicted loss-of-function (LoFs) variants defined as stop-gain, frame shift, initiation codon (INIT) and splice site mutations (n = 930, OR = 1.3, P = 1.5×E-5). There was no enrichment across all rare protein altering variants defined as missense plus LoFs, in frame indels and stop-loss variants (n = 13 014, OR = 0.97, P = 0.47). Among LoFs, the strongest burden was observed for INIT (OR = 2.16, P = 0.0097) and premature stop variants predicted to cause non-sense-mediated decay in the majority of transcripts (NMD) (OR = 1.98, P = 0.02). Notably, this increased burden of NMD, INIT and splice variants was more pronounced in a set of 1397 innate immune genes (OR = 4.55, P = 0.0043). Further comparison to additional exomes indicates that the difference in LoF burden originated both from the AD and centenarian sample. In summary, we observed an overall increased burden of rare LoFs in AD subjects as compared to centenarians, and this enrichment is more pronounced for innate immune genes.

Altered Levels of Visinin-Like Protein 1 Correspond to Regional Neuronal Loss in Alzheimer Disease and Frontotemporal Lobar Degeneration.

Recent studies have implicated the neuronal calcium-sensing protein visinin-like 1 protein (Vilip-1) as a peripheral biomarker in Alzheimer disease (AD), but little is known about expression of Vilip-1 in the brains of patients with AD. We used targeted and quantitative mass spectrometry to measure Vilip-1 peptide levels in the entorhinal cortex (ERC) and the superior frontal gyrus (SF) from cases with early to moderate stage AD, frontotemporal lobar degeneration (FTLD), and cognitively and neuropathologically normal elderly controls. We found that Vilip-1 levels were significantly lower in the ERC, but not in SF, of AD subjects compared to normal controls. In FTLD cases, Vilip-1 levels in the SF were significantly lower than in normal controls. These findings suggest a unique role for cerebrospinal fluid Vilip-1 as a biomarker of ERC neuron loss in AD.

Haloperidol inactivates AMPK and reduces tau phosphorylation in a tau mouse model of Alzheimer's disease.

INTRODUCTION: The use of antipsychotic medications in Alzheimer's disease has been associated with an increased risk of mortality in clinical trials. However, an older postmortem literature suggests that those with schizophrenia treated in an era of exclusively conventional antipsychotic medications had a surprisingly low incidence of tau pathology. No previously published studies have investigated the impact of conventional antipsychotic exposure on tau outcomes in a tau mouse model of AD. METHODS: In two experiments, transgenic rTg (tauP301L) 4510 tau mice were treated with either haloperidol or vehicle and phosphotau epitopes were quantified using high-sensitivity tau ELISA. RESULTS: After treatments of 2 and 6 week's duration, mice treated with haloperidol evidenced a significant reduction in tau phosphorylation associated with an inactivation of the tau kinase AMPK. DISCUSSION: The data suggest that D2 receptor blockade reduces tau phosphorylation in vivo. Future studies are necessary to investigate the impact of this reduction on tau neuropathology.

Cannabinoid CB2 Receptors in a Mouse Model of Aß Amyloidosis: Immunohistochemical Analysis and Suitability as a PET Biomarker of Neuroinflammation.

In Alzheimer's disease (AD), one of the early responses to Aß amyloidosis is recruitment of microglia to areas of new plaque. Microglial receptors such as cannabinoid receptor 2 (CB2) might be a suitable target for development of PET radiotracers that could serve as imaging biomarkers of Aß-induced neuroinflammation. Mouse models of amyloidosis (J20APPswe/ind and APPswe/PS1ΔE9) were used to investigate the cellular distribution of CB2 receptors. Specificity of CB2 antibody (H60) was confirmed using J20APPswe/ind mice lacking CB2 receptors. APPswe/PS1ΔE9 mice were used in small animal PET with a CB2-targeting radiotracer, [11C]A836339. These studies revealed increased binding of [11C]A836339 in amyloid-bearing mice. Specificity of the PET signal was confirmed in a blockade study with a specific CB2 antagonist, AM630. Confocal microscopy revealed that CB2-receptor immunoreactivity was associated with astroglial (GFAP) and, predominantly, microglial (CD68) markers. CB2 receptors were observed, in particular, in microglial processes forming engulfment synapses with Aß plaques. In contrast to glial cells, neuron (NeuN)-derived CB2 signal was equal between amyloid-bearing and control mice. The pattern of neuronal CB2 staining in amyloid-bearing mice was similar to that in human cases of AD. The data collected in this study indicate that Aß amyloidosis without concomitant tau pathology is sufficient to activate CB2 receptors that are suitable as an imaging biomarker of neuroinflammation. The main source of enhanced CB2 PET binding in amyloid-bearing mice is increased CB2 immunoreactivity in activated microglia. The presence of CB2 immunoreactivity in neurons does not likely contribute to the enhanced CB2 PET signal in amyloid-bearing mice due to a lack of significant neuronal loss in this model. However, significant loss of neurons as seen at late stages of AD might decrease the CB2 PET signal due to loss of neuronally-derived CB2. Thus this study in mouse models of AD indicates that a CB2-specific radiotracer can be used as a biomarker of neuroinflammation in the early preclinical stages of AD, when no significant neuronal loss has yet developed.

Haloperidol and sudden cardiac death in dementia: autopsy findings in psychiatric inpatients.

OBJECTIVE: Treatment with haloperidol has been shown, in studies using death certificates and prescription files, to be associated with an excess of sudden cardiac deaths, and regulatory warnings highlight this risk in patients with dementia. We used autopsy findings to determine whether the rate of sudden cardiac death is greater in cases of unexpected deaths of patients with dementia treated with haloperidol. METHODS: From 1989 through 2013, 1219 patients with a primary diagnosis of dementia with behavioral disturbance were admitted to a psychiatric hospital, and 65 (5.3%) died suddenly. Sixty-five patients (5.3%) died unexpectedly. Complete post-mortem examinations after the sudden death were performed in 55 (84.6%) patients. Twenty-seven of the autopsied cases (49.1%) had been treated with haloperidol orally (2.2 mg ± 2.1 mg/day), the only antipsychotic used in this cohort. Univariable comparisons and multivariable regression analyses compared the groups of patients with or without sudden cardiac death. RESULTS: The leading causes of death were sudden cardiac death (32.7%), myocardial infarction (25.5% of patients), pneumonia (23.6%), and stroke (10.9%). Patients with sudden cardiac death and those with anatomically established cause of death were similar regarding the use of haloperidol (p = 0.5). Sudden cardiac death patients were more likely to suffer from Alzheimer's dementia (p = 0.027) and to have a past history of heart disease (p = 0.0094), and less likely to have been treated with a mood stabilizer (p = 0.024), but none of these variables were independent predictors of sudden cardiac death. CONCLUSION: Autopsy data suggest that oral haloperidol is not associated with increased risk of sudden cardiac death in psychiatric inpatients with dementia.

Optimal treatment of Alzheimer's disease psychosis: challenges and solutions.

Psychotic symptoms emerging in the context of neurodegeneration as a consequence of Alzheimer's disease was recognized and documented by Alois Alzheimer himself in his description of the first reported case of the disease. Over a quarter of a century ago, in the context of attempting to develop prognostic markers of disease progression, psychosis was identified as an independent predictor of a more-rapid cognitive decline. This finding has been subsequently well replicated, rendering psychotic symptoms an important area of exploration in clinical history taking - above and beyond treatment necessity - as their presence has prognostic significance. Further, there is now a rapidly accreting body of research that suggests that psychosis in Alzheimer's disease (AD+P) is a heritable disease subtype that enjoys neuropathological specificity and localization. There is now hope that the elucidation of the neurobiology of the syndrome will pave the way to translational research eventuating in new treatments. To date, however, the primary treatments employed in alleviating the suffering caused by AD+P are the atypical antipsychotics. These agents are approved by the US Food and Drug Administration for the treatment of schizophrenia, but they have only marginal efficacy in treating AD+P and are associated with troubling levels of morbidity and mortality. For clinical approaches to AD+P to be optimized, this syndrome must be disentangled from other primary psychotic disorders, and recent scientific advances must be translated into disease-specific therapeutic interventions. Here we provide a review of atypical antipsychotic efficacy in AD+P, followed by an overview of critical neurobiological observations that point towards a frontal, tau-mediated model of disease, and we suggest a new preclinical animal model for future translational research.

Disease variants in genomes of 44 centenarians.

To identify previously reported disease mutations that are compatible with extraordinary longevity, we screened the coding regions of the genomes of 44 Ashkenazi Jewish centenarians. Individual genome sequences were generated with 30× coverage on the Illumina HiSeq 2000 and single-nucleotide variants were called with the genome analysis toolkit (GATK). We identified 130 coding variants that were annotated as "pathogenic" or "likely pathogenic" based on the ClinVar database and that are infrequent in the general population. These variants were previously reported to cause a wide range of degenerative, neoplastic, and cardiac diseases with autosomal dominant, autosomal recessive, and X-linked inheritance. Several of these variants are located in genes that harbor actionable incidental findings, according to the recommendations of the American College of Medical Genetics. In addition, we found risk variants for late-onset neurodegenerative diseases, such as the APOE ε4 allele that was even present in a homozygous state in one centenarian who did not develop Alzheimer's disease. Our data demonstrate that the incidental finding of certain reported disease variants in an individual genome may not preclude an extraordinarily long life. When the observed variants are encountered in the context of clinical sequencing, it is thus important to exercise caution in justifying clinical decisions.

Psychotic Alzheimer's disease is associated with gender-specific tau phosphorylation abnormalities.

Converging evidence suggests that psychotic Alzheimer's disease (AD + P) is associated with an acceleration of frontal degeneration, with tau pathology playing a primary role. Previous histopathologic and biomarker studies have specifically implicated tau pathology in this condition. To precisely quantify tau abnormalities in the frontal cortex in AD + P, we used a sensitive biochemical assay of total tau and 4 epitopes of phospho-tau relevant in AD pathology in a postmortem sample of AD + P and AD - P. Samples of superior frontal gyrus from 26 AD subjects without psychosis and 45 AD + P subjects with psychosis were analyzed. Results of enzyme-linked immunosorbent assay demonstrate that AD + P females, but not males, had significantly higher levels of phosphorylated tau in the frontal cortex. In males, but not females, AD + P was associated with the presence of α-synuclein pathology. These results support a gender dissociation of pathology in AD + P. The design of future studies aimed at the elucidation of cognitive and/or functional outcomes; regional brain metabolic deficits; or genetic correlates of AD + P should take gender into consideration.

CB2 receptor deficiency increases amyloid pathology and alters tau processing in a transgenic mouse model of Alzheimer's disease.

The endocannabinoid CB2 receptor system has been implicated in the neuropathology of Alzheimer's disease (AD). In order to investigate the impact of the CB2 receptor system on AD pathology, a colony of mice with a deleted CB2 receptor gene, CNR2, was established on a transgenic human mutant APP background for pathological comparison with CB2 receptor-sufficient transgenic mice. J20 APP (PDGFB-APPSwInd) mice were bred over two generations with CNR2(-/-) (Cnr2(tm1Dgen)/J) mice to produce a colony of J20 CNR2(+/+) and J20 CNR2(-/-) mice. Seventeen J20 CNR2(+/+) mice (12 females, 5 males) and 16 J20 CNR2(-/-) mice (11 females, 5 males) were killed at 12 months, and their brains were interrogated for AD-related pathology with both biochemistry and immunocytochemistry (ICC). In addition to amyloid-dependent endpoints such as soluble Aß production and plaque deposition quantified with 6E10 staining, the effect of CB2 receptor deletion on total soluble mouse tau production was assayed by using a recently developed high-sensitivity assay. Results revealed that soluble Aß42 and plaque deposition were significantly increased in J20 CNR2(-/-) mice relative to CNR2(+/+) mice. Microgliosis, quantified with ionized calcium-binding adapter molecule 1 (Iba-1) staining, did not differ between groups, whereas plaque associated microglia was more abundant in J20 CNR2(-/-) mice. Total tau was significantly suppressed in J20 CNR2(-/-) mice relative to J20 CNR2(+/+) mice. The results confirm the constitutive role of the CB2 receptor system both in reducing amyloid plaque pathology in AD and also support tehpotential of cannabinoid therapies targeting CB2 to reduce Aß; however, the results suggest that interventions may have a divergent effect on tau pathology.