Persistent depressive symptoms are associated with frontal regional atrophy in patients with Alzheimer's disease.

BACKGROUND: Depression in individuals with Alzheimer's disease (AD) is common, difficult to treat and inadequately understood. Previous studies have identified possible differences in regional brain atrophy in individuals with AD and depression, but the results have been inconsistent and some studies had less robust definitions of depression. We aimed to examine regional brain atrophy in two large dementia focused cohorts. METHODS: We used data from Alzheimer's disease neuroimaging initiative (ADNI) and the National Alzheimer's Co-ordinating Center (NACC), for those with data from at least one MRI scan. Depression ratings were available using the Geriatric Depression Scale (GDS) and Neuropsychiatric Inventory (NPI). Intermittent depressive symptoms were defined as one episode above threshold (≥8 on GDS, ≥6 on NPI depression subscale and ≥2 on the Neuropsychiatric Inventory version Q depression sub-scale) and persistent as ≥2 episodes. Derived regional volumetric data was available from ADNI and the NACC. RESULTS: Data was available from 698 individuals with AD in NACC and from 666 individuals in ADNI. We found no evidence of between group differences in regional brain volume at baseline, or of differential atrophy in NACC. In ADNI we found evidence of increased brain atrophy in several frontal brain areas. LIMITATIONS: Because this study was limited to those with MRI data, the numbers in some analyses were low. MRI parcellation differed between studies making direct comparison difficult. For some individuals only the NPI was used to rate depression. CONCLUSIONS: We have found mixed evidence of increased regional atrophy in depression in AD, mainly in frontal brain regions. We found no evidence to support a vascular basis for depression in AD.

Ras-ERK-ETS inhibition alleviates neuronal mitochondrial dysfunction by reprogramming mitochondrial retrograde signaling.

Mitochondrial dysfunction activates the mitochondrial retrograde signaling pathway, resulting in large scale changes in gene expression. Mitochondrial retrograde signaling in neurons is poorly understood and whether retrograde signaling contributes to cellular dysfunction or is protective is unknown. We show that inhibition of Ras-ERK-ETS signaling partially reverses the retrograde transcriptional response to alleviate neuronal mitochondrial dysfunction. We have developed a novel genetic screen to identify genes that modify mitochondrial dysfunction in Drosophila. Knock-down of one of the genes identified in this screen, the Ras-ERK-ETS pathway transcription factor Aop, alleviates the damaging effects of mitochondrial dysfunction in the nervous system. Inhibition of Ras-ERK-ETS signaling also restores function in Drosophila models of human diseases associated with mitochondrial dysfunction. Importantly, Ras-ERK-ETS pathway inhibition partially reverses the mitochondrial retrograde transcriptional response. Therefore, mitochondrial retrograde signaling likely contributes to neuronal dysfunction through mis-regulation of gene expression.

Evaluation of the efficacy of pimavanserin in the treatment of agitation and aggression in patients with Alzheimer's disease psychosis: A post hoc analysis.

OBJECTIVES: Patients with Alzheimer's disease psychosis (ADP) commonly experience concomitant agitation and aggression. We investigated whether a reduction in ADP following pimavanserin treatment conferred a reduction in associated agitation and aggression. METHODS: ACP-103-019 was a 12-week, randomized, double-blind, placebo-controlled study that evaluated the efficacy of pimavanserin (34 mg) in reducing psychotic symptoms in patients with ADP. The primary endpoint was change from baseline in Neuropsychiatric Inventory-Nursing Home Version-Psychosis Score (NPI-NH-PS) at week six. A post hoc analysis examined whether there was a greater reduction in agitation and aggression (NPI-NH domain C [agitation/aggression] and Cohen-Mansfield Agitation Inventory-Short Form [CMAI-SF]) in pimavanserin-treated patients who experienced a reduction of hallucinations and delusions (psychosis responders defined as ≥50% reduction from baseline in NPI-NH-PS, week six) when compared with those who did not (nonresponders). RESULTS: Pimavanserin-treated patients with ≥50% response in psychotic symptoms (n = 44) showed a greater improvement in agitation and aggression symptoms on the NPI-NH domain C (week six, least squares mean [LSM] difference = -3.64, t = -4.69, P < .0001) and the CMAI-SF (week six, LSM difference = -3.71, t = -2.01, P = .0483) than nonresponders (n = 32). Differences between psychosis responders and nonresponders were also observed in patients with more severe agitation and aggression at baseline on the NPI-NH domain C (responders, n = 26; nonresponders, n = 13; week six, LSM difference = -3.03, t = -2.44, P = .019). CONCLUSIONS: Patients with ADP, who show improvement in psychotic symptoms after pimavanserin treatment, also experience an improvement in concomitant agitation and aggression.

Dementia in Parkinson's disease is associated with enhanced mitochondrial complex I deficiency.

BACKGROUND: Dementia is a common feature of Parkinson's disease (PD), but the neuropathological changes associated with the development of Parkinson's disease dementia (PDD) are only partially understood. Mitochondrial dysfunction is a hallmark of PD but has not been studied in PDD. METHODS: Molecular and biochemical approaches were used to study mitochondrial activity and quantity in postmortem prefrontal cortex tissue. Tissues from pathologically confirmed PD and PDD patients and from age-matched controls were used to analyze the activity of mitochondrial enzyme complex nicotinamide adenine dinucleotide:ubiquinone oxidoreductase, or complex I (the first enzyme in the mitochondrial respiratory chain), mitochondrial DNA levels, and the expression of mitochondrial proteins. RESULTS: Complex I activity was significantly decreased (27% reduction; analysis of variance with Tukey's post hoc test; P < 0.05) in PDD patients, and mitochondrial DNA levels were also significantly decreased (18% reduction; Kruskal-Wallis analysis of variance with Dunn's multiple comparison test; P < 0.05) in PDD patients compared with controls, but neither was significantly reduced in PD patients. Overall, mitochondrial biogenesis was unaffected in PD or PDD, because the expression of mitochondrial proteins in patients was similar to that in controls. CONCLUSIONS: Patients with PDD have a deficiency in mitochondrial complex I activity and reduced mitochondrial DNA levels in the prefrontal cortex without a change in mitochondrial protein quantity. Therefore, mitochondrial complex I deficiency and reduced mitochondrial DNA in the prefrontal cortex may be a hallmark of dementia in patients with PD.

Putting brain training to the test.

'Brain training', or the goal of improved cognitive function through the regular use of computerized tests, is a multimillion-pound industry, yet in our view scientific evidence to support its efficacy is lacking. Modest effects have been reported in some studies of older individuals and preschool children, and video-game players outperform non-players on some tests of visual attention. However, the widely held belief that commercially available computerized brain-training programs improve general cognitive function in the wider population in our opinion lacks empirical support. The central question is not whether performance on cognitive tests can be improved by training, but rather, whether those benefits transfer to other untrained tasks or lead to any general improvement in the level of cognitive functioning. Here we report the results of a six-week online study in which 11,430 participants trained several times each week on cognitive tasks designed to improve reasoning, memory, planning, visuospatial skills and attention. Although improvements were observed in every one of the cognitive tasks that were trained, no evidence was found for transfer effects to untrained tasks, even when those tasks were cognitively closely related.

Decreased immunoreactivities of neocortical AMPA receptor subunits correlate with motor disability in Lewy body dementias.

Dementia with Lewy bodies and Parkinson's disease dementia are different clinical phenotypes of Lewy body dementias differentiated by the temporal relationship between parkinsonism and dementia onset. At present, it is unclear whether the glutamatergic system is affected in these disorders. In this study, we measured α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor GluA subunits in the postmortem neocortex of a cohort of prospectively studied Lewy body dementia cases, as well as age-matched controls by immunoblotting. We found losses of GluA2/3/4 immunoreactivities in Lewy body dementias which correlated with higher pre-death Hoehn and Yahr scores and with longer Parkinson's disease duration before dementia onset, but not with dementia severity, cortical Lewy body burden, or amyloid plaque and neurofibrillary tangle burden. Our study suggests that GluA2/3/4 losses may be a neurochemical marker of motor disability in Lewy body dementias.

Characterization of Depressive Symptoms in Dementia and Examination of Possible Risk Factors.

Background: Depression in individuals with Alzheimer's disease (AD) is common, distressing, difficult to treat, and inadequately understood. It occurs more frequently in AD than in older adults without dementia. The reasons why some patients develop depression during AD and others do not remain obscure. Objective: We aimed to characterize depression in AD and to identify risk factors. Methods: We used data from three large dementia focused cohorts: ADNI (n = 665 with AD, 669 normal cognition), NACC (n = 698 with AD, 711 normal cognition), and BDR (n = 757 with AD). Depression ratings were available using the GDS and NPI and in addition for BDR the Cornell. A cut-off of≥8 was used for the GDS and the Cornell Scale for Depression in Dementia,≥6 for the NPI depression sub-scale, and≥2 for the NPI-Q depression sub-scale. We used logistic regression to examine potential risk factors and random effects meta-analysis and an interaction term to look for interactions between each risk factor and the presence of cognitive impairment. Results: In individual studies there was no evidence of a difference in risk factors for depressive symptoms in AD. In the meta-analysis the only risk factor which increased the risk of depressive symptoms in AD was previous depression, but information on this was only available from one study (OR 7.78 95% CI 4.03-15.03). Conclusion: Risk factors for depression in AD appear to differ to those for depression per se supporting suggestions of a different pathological process, although a past history of depression was the strongest individual risk factor.

Dementia with Lewy Bodies Drug Therapies in Clinical Trials: Systematic Review up to 2022.

INTRODUCTION: Reviews of randomized clinical trials (RCTs) in dementia with Lewy bodies (DLB) are essential for informing ongoing research efforts of symptomatic therapies and potentially disease-modifying therapies (DMTs). METHODS: We performed a systematic review of all clinical trials conducted until September 27, 2022, by examining 3 international registries: ClinicalTrials.gov, the European Union Drug Regulating Authorities Clinical Trials Database, and the International Clinical Trials Registry Platform, to identify drugs in trials in DLB. RESULTS: We found 25 agents in 40 trials assessing symptomatic treatments and DMTs for DLB: 7 phase 3, 31 phase 2, and 2 phase 1 trials. We found an active pipeline for drug development in DLB, with most ongoing clinical trials in phase 2. We identified a recent trend towards including participants at the prodromal stages, although more than half of active clinical trials will enroll mild to moderate dementia patients. Additionally, repurposed agents are frequently tested, representing 65% of clinical trials. CONCLUSION: Current challenges in DLB clinical trials include the need for disease-specific outcome measures and biomarkers, and improving representation of global and diverse populations.

Proteasome inhibition leads to early loss of synaptic proteins in neuronal culture.

A dysfunctional ubiquitin proteasome system may be a mediating factor of disease progression in Lewy body dementia (LBD). The effects of proteasome inhibition using lactacystin and epoxomicin in primary neuronal culture were studied to assess the validity of this model to reflect the cortical pathology of LBD. Treatment of primary cortical neurons with 5 µM lactacystin for 24 h led to a 38 % reduction in the levels of ß-III-tubulin (p < 0.05), a 48 % reduction in the levels of synaptophysin (p < 0.05) and a 74 % reduction in the levels of drebrin (p < 0.01), when compared to controls. Results for epoxomicin were similar. The loss of neuronal protein occurred prior to any loss of mitochondrial activity or cell death. The results are reflective of the loss of synapses and the synaptic changes observed in LBD, which may be an early event in the neurodegeneration of LBD. The similarities with the pathological changes in LBD highlight the possibility that this model can potentially provide a platform to test novel treatments.

Neurogenic marker abnormalities in the hippocampus in dementia with Lewy bodies.

Dementia with Lewy bodies (DLB) is associated with alpha synuclein pathology and slowly progressive dementia. Progenitor abnormalities have previously been reported in the subventricular zone (SVZ) adjacent to the lateral ventricle. To evaluate changes in neural stem cells and progenitors in the hippocampal neurogenic niche, immunohistochemistry (IHC) using the neural stem cell markers Musashi 1, nestin, proliferating cell nuclear antigen (PCNA), doublecortin, and glial fibrillary acidic protein (GFAP) were examined in age-matched control and DLB groups. Staining was quantified in the hippocampal SVZ, subgranular layer (SGL) and ependymal cell layer (EPL). There was a significant loss in DLB of Musashi 1 (P < 0.01) in all areas, an increase in PCNA in hippocampal SVZ (P = 0.01) and SGL (P = 0.05), and an increase in doublecortin in the hippocampal SVZ (P = 0.04) and EPL (P = 0.02). This is the first report of the changes in neurogenic markers in the hippocampal SVZ and EPL in DLB and may offer the potential for understanding disease pathology and in the devising of treatment.

Genetic associations of autopsy-confirmed vascular dementia subtypes.

BACKGROUND/AIMS: Genetic risk factors have not been clearly established for vascular dementias (VaD) related to stroke and cerebrovascular disease. METHODS: Samples were genotyped for APOE, MTHFR and ICAM. Aß levels and choline acetyltransferase (ChAT) activities were assayed in controls and individuals with VaD. RESULTS: Associations were found between the APOE-ε4 allele and mixed dementia, infarct/stroke dementia and subcortical ischemic vascular dementia (SIVD), and higher Aß1-42 levels and decreased ChAT activity. MTHFR was more associated with SIVD, mixed dementia, and lower ChAT activity. CONCLUSIONS: The study demonstrates important differences in the genetic associations of VaD and begins to clarify the genetic basis of key pathological substrates.

Antipsychotic medication is associated with selective alterations in ventricular cerebrospinal fluid Aß 40 and tau in patients with intractable unipolar depression.

OBJECTIVE: Alterations in plasma and in lumbar cerebrospinal fluid amyloid-B peptide (Aß) levels have been reported in Alzheimer's disease. Studies have also suggested similar changes in depressed patients. No information is available on the impact of psychotropic drugs on this in patients with depression. We therefore quantified Aß in ventricular cerebrospinal fluid (CSF) in a population of patients with treatment-resistant depression, with and without antipsychotic medication. METHOD: A cross-sectional study of 32 patients undergoing subcaudate tractotomy for major (unipolar) depressive disorder. Ventricular CSF concentrations of Aß peptide 1-40 and 1-42, also p-tau and total tau were determined by Western blotting or enzyme-linked immunosorbent assay. RESULTS: Patients taking antipsychotic medication in the 2 weeks prior to surgery demonstrated significantly higher levels of Aß 1-40 (mean ± SD: 727.3 ± 382.3 vs. 440.9 ± 337.2 pg/ml; p = 0.032, Student's t-test) but unaltered Aß 1-42 (mean 72.1 ± 67.5 vs. 60.0 ± 56.7 pg/ml; p = 0.587) compared to a matched sample not treated with antipsychotic drugs. The same group demonstrated elevated total tau (mean 945.0 ± 422.2 vs. 534.3 ± 388.3 pg/ml; p = 0.010) but not p-tau (mean 98.6 ± 71.5 vs. 88.1 ± 70.5 pg/ml; p = 0.694). No similar effect was found with lithium, antidepressants, carbamazepine or benzodiazepines. CONCLUSIONS: This preliminary study suggests antipsychotic drugs, widely used in patients with severe depression across all age ranges, may be associated with alteration of Aß 1-40 and total tau, indices strongly linked with progressive organic brain disease. Further confirmatory work is needed.

Efficacy results of pimavanserin from a multi-center, open-label extension study in Parkinson's disease psychosis patients.

INTRODUCTION: Pimavanserin, a selective 5-HT2A inverse agonist/antagonist, was approved for hallucinations and delusions associated with Parkinson's disease psychosis (PDP). We present durability of response with pimavanserin in patients with PDP for an additional 4 weeks of treatment. METHODS: This was an open-label extension (OLE) study in patients previously completing one of three double-blind, placebo-controlled (Core) studies. All patients received pimavanserin 34 mg once daily. Efficacy assessments included the Scale for the Assessment of Positive Symptoms (SAPS) PD and H + D scales, Clinical Global Impression (CGI) Improvement and Severity scales and Caregiver Burden Scale (CBS), through 4 weeks in the OLE. Safety assessments were conducted at each visit. RESULTS: Of 459 patients, 424 (92.4%) had a Week 4 efficacy assessment. At Week 4 (10 weeks total treatment), SAPS-PD mean (standard deviation) change from OLE baseline was -1.8 (5.5) and for SAPS-H + D was -2.1 (6.2) with pimavanserin 34 mg. Patients receiving placebo during the Core studies had greater improvements (SAPS-PD -2.9 [5.6]; SAPS-H + D -3.5 [6.3]) during the OLE. For participants treated with pimavanserin 8.5 or 17 mg during the Core studies, further improvement was observed during the OLE with pimavanserin 34 mg. The mean change from Core Study baseline for SAPS-PD score was similar among prior pimavanserin 34 mg and prior placebo-treated participants (-7.1 vs. -7.0). The CGI-I response rate (score of 1 or 2) at Week 4 was 51.4%. Adverse events were reported by 215 (46.8%) patients during the first 4 weeks of OLE. The most common AEs were fall (5.9%), hallucination (3.7%), urinary tract infection (2.8%), insomnia (2.4%), and peripheral edema (2.2%) CONCLUSIONS: Patients previously on pimavanserin 34 mg during three blinded core studies had durability of efficacy during the subsequent 4 week OLE SAPS-PD assessment. Patients previously on blinded placebo improved after 4 weeks of OL pimavanserin treatment. These results in over 400 patients from 14 countries support the efficacy of pimavanserin for treating PDP.

Donepezil for the treatment of agitation in Alzheimer's disease.

BACKGROUND: Agitation is a common and distressing symptom in patients with Alzheimer's disease. Cholinesterase inhibitors improve cognitive outcomes in such patients, but the benefits of these drugs for behavioral disturbances are unclear. METHODS: We randomly assigned 272 patients with Alzheimer's disease who had clinically significant agitation and no response to a brief psychosocial treatment program to receive 10 mg of donepezil per day (128 patients) or placebo (131 patients) for 12 weeks. The primary outcome was a change in the score on the Cohen-Mansfield Agitation Inventory (CMAI) (on a scale of 29 to 203, with higher scores indicating more agitation) at 12 weeks. RESULTS: There was no significant difference between the effects of donepezil and those of placebo on the basis of the change in CMAI scores from baseline to 12 weeks (estimated mean difference in change [the value for donepezil minus that for placebo], -0.06; 95% confidence interval [CI], -4.35 to 4.22). Twenty-two of 108 patients (20.4%) in the placebo group and 22 of 113 (19.5%) in the donepezil group had a reduction of 30% or greater in the CMAI score (the value for donepezil minus that for placebo, -0.9 percentage point; 95% CI, -11.4 to 9.6). There were also no significant differences between the placebo and donepezil groups in scores for the Neuropsychiatric Inventory, the Neuropsychiatric Inventory Caregiver Distress Scale, or the Clinician's Global Impression of Change. CONCLUSIONS: In this 12-week trial, donepezil was not more effective than placebo in treating agitation in patients with Alzheimer's disease. (ClinicalTrials.gov number, NCT00142324 [ClinicalTrials.gov].).

Increased binding to 5-HT1A and 5-HT2A receptors is associated with large vessel infarction and relative preservation of cognition.

Vascular dementia accounts for approximately 15-20% of all dementias. In addition, a significant subset of people with Alzheimer's disease have concurrent cerebrovascular disease. Vascular dementia is caused by different cerebrovascular morphological abnormalities including large artery territory infarction (multi-infarct vascular dementia) and sub-cortical ischaemic vascular dementia. Despite this distinction, there is a lack of studies examining the neurochemistry of individual vascular dementia subtypes. Serotonin is believed to play an important role in cognition, and serotonin receptors may provide a novel target for future anti-dementia therapeutics. This study aimed to determine levels of two serotonin receptors in subtypes of vascular dementia and relate any changes to cognition. We have determined, using saturation radioligand binding, the binding parameters (affinity and maximal binding) of ((3)H)-WAY 100635 binding to 5-HT(1A) receptors and ((3)H)-ketanserin binding to 5-HT(2A) receptors in post-mortem tissue from the frontal and temporal cortices of patients with either multi-infarct vascular dementia, sub-cortical ischaemic vascular dementia, mixed Alzheimer's disease/vascular dementia or stroke no dementia (SND). 5-HT(1A) and 5-HT(2A) receptor binding was significantly increased in the temporal cortex of patients with either multi-infarct vascular dementia or SND, compared to age-matched controls. 5-HT(1A) receptor maximal binding in the temporal cortex was also positively correlated with cognition as determined by Mini-Mental State Examination (MMSE) and Cambridge Assessment of Mental Health for the Elderly scores (CAMCOG). These results reveal an important distinction between the neurochemistry of multi-infarct vascular dementia/SND and sub-cortical ischaemic vascular dementia, suggesting that pharmacological manipulation of serotonin offers the possibility to develop novel therapies for stroke and multi-infarct vascular dementia patients. The results also highlight the importance of the cortical 5-HT(1A) receptor in mediating cognition.

Temporal Relationship Between Depressive Symptoms and Cognition in Mid and Late Life: A Longitudinal Cohort Study.

OBJECTIVES: To examine the bidirectional temporal relationship between depressive symptoms and cognition in relation to risk, reaction, and prodrome. DESIGN: Cross-lag analysis of longitudinal data collected online at baseline and 12-month follow-up. SETTING AND PARTICIPANTS: A United Kingdom population cohort of 11,855 participants aged 50 years and over. MEASURES: Patient Health Questionnaire-9 (depressive symptoms), cognitive measures: Paired Associate Learning, Verbal Reasoning, Spatial Working Memory, and Digit Span. RESULTS: Depressive symptoms predicted a decline in paired associates learning [ß = -.020, P = .013, (95% confidence interval [CI], ‒.036, -.004)] and verbal reasoning [ß = -.014, P = .016, (95% CI ‒.025, -.003)] but not vice versa. Depressive symptoms predicted [ß = -.043, P < .001, (95% CI ‒.060, -.026); ß = -.029, P < .001, (95% CI ‒.043, -.015)] and were predicted by [ß = -.030, P = < .001, (95% CI ‒.047, -.014); ß = -.025, P = .003, (95% CI ‒.041, -.009)], a decline in spatial working memory and verbal digit span, respectively. CONCLUSIONS AND IMPLICATIONS: Depressive symptoms may be either a risk factor or prodrome for cognitive decline. In addition, a decline in attention predicts depressive symptoms. Clinical implications and implications for further research are discussed.

Long-term evaluation of open-label pimavanserin safety and tolerability in Parkinson's disease psychosis.

INTRODUCTION: Pimavanserin is a selective 5-HT2A inverse agonist/antagonist approved for treating hallucinations and delusions associated with Parkinson's disease psychosis (PDP). Results from short-term, placebo-controlled studies demonstrated a positive benefit/risk profile. This multi-year, open-label study assessed long-term safety and tolerability of pimavanserin. METHODS: This was an open-label extension (OLE) study in patients previously completing a double-blind, placebo-controlled study or a previous OLE study. Safety was evaluated from adverse events (AEs), clinical laboratory results, motor symptoms, electrocardiograms (ECG), and mortality. Durability of response was assessed from the Clinical Global Impression-Severity (CGI-S) scale and Caregiver Burden Scale (CBS). RESULTS: Of 459 participants treated in this OLE study (average age 71.2 years), the median duration of treatment was 454 days. Over the entire study period (approximately 11 years), ≥1 AE occurred in 392 (85.4%) patients; the majority were of mild to moderate intensity, with fall (32.0%), urinary tract infection (19.0%), and hallucination (13.7%) most common. Serious AEs occurred in 188 (41.0%) patients, and an AE leading to study termination or dose discontinuation occurred in 133 (29.0%) patients. Sixty-one patients died, 59 (12.9%) during treatment or within 30 days after the last dose of study drug; the observed mortality rate was 6.45 per 100 patient-years of exposure. Mean scores for the CGI-S scale and CBS generally remained stable for up to 192 weeks (>3.5 years). CONCLUSIONS: Long-term treatment with pimavanserin 34 mg once daily demonstrated a favorable benefit/risk profile with no unexpected safety concerns. Mortality rates suggested no increased risk following long-term treatment.

Patterns of Mitochondrial TSPO Binding in Cerebral Small Vessel Disease: An in vivo PET Study With Neuropathological Comparison.

Small vessel disease (SVD) is associated with cognitive impairment in older age and be implicated in vascular dementia. Post-mortem studies show proliferation of activated microglia in the affected white matter. However, the role of inflammation in SVD pathogenesis is incompletely understood and better biomarkers are needed. We hypothesized that expression of the 18 kDa translocator protein (TSPO), a marker of microglial activation, would be higher in SVD. Positron emission tomography (PET) was performed with the second-generation TSPO ligand [11C]PBR28 in 11 participants with SVD. TSPO binding was evaluated by a two-tissue compartment model, with and without a vascular binding component, in white matter hyperintensities (WMH) and normal-appearing white matter (NAWM). In post-mortem tissue, in a separate cohort of individuals with SVD, immunohistochemistry was performed for TSPO and a pan-microglial marker Iba1. Kinetic modeling showed reduced tracer volume and blood volume fraction in WMH compared with NAWM, but a significant increase in vascular binding. Vascular [11C]PBR28 binding was also increased compared with normal-appearing white matter of healthy participants free of SVD. Immunohistochemistry showed a diffuse increase in microglial staining (with Iba1) in sampled tissue in SVD compared with control samples, but with only a subset of microglia staining positively for TSPO. Intense TSPO staining was observed in the vicinity of damaged small blood vessels, which included perivascular macrophages. The results suggest an altered phenotype of activated microglia, with reduced TSPO expression, in the areas of greatest white matter ischemia in SVD, with implications for the interpretation of TSPO PET studies in older individuals or those with vascular risk factors.

Amyloid beta concentrations in older people with Down syndrome and dementia.

People with Down syndrome develop Alzheimer's disease with an early age of onset. Plasma amyloid beta (Abeta) levels were measured in individuals with Down syndrome who were over the age of 40. No associations between age and Abeta1-40 and Abeta1-42 concentrations were found and nor were Abeta1-40 and Abeta1-42 levels found to vary between those with Alzheimer's-type dementia and those without dementia. The APOE genotype was not found to have an impact upon Abeta1-40 or Abeta1-42 concentrations. These data suggest that other factors play important roles in determining the onset and progression of dementia in the Down syndrome population.

Choline acetyltransferase activity in vascular dementia and stroke.

BACKGROUND/AIM: Alterations in cholinergic activity have not been systematically studied in types of cerebrovascular disease. We examined cholinergic function at postmortem, focussing on stroke and vascular dementia (VaD). METHODS: Post-mortem brain tissue was studied from 61 patients with stroke or VaD (13 infarct dementia; 8 stroke/no dementia; 11 sub-cortical ischaemic VaD, SIVD; 29 VaD and concurrent Alzheimer's disease, AD), 12 patients with AD and 23 controls. Choline acetyltransferase (ChAT) was measured in Brodmann areas (BA) 9 and 20/21. RESULTS: There were significant reductions in ChAT activity in patients with VaD and concurrent AD compared to age-matched controls (BA9: t = 2.7, p = 0.009; BA20/21: t = 4.67, p = 0.000). In patients with infarct dementia, there was a significant 27% increase in ChAT activity in BA9 (t = 2.1, p = 0.047), but not in BA20/21 (t = 1.67, p = 0.106), compared to the age-matched control group. There was no relationship between ChAT activity and cognition in the VaD patients. CONCLUSIONS: Loss of cholinergic function is only evident in VaD patients with concurrent AD. A novel increase in cholinergic activity was identified in patients with infarct dementia, which may create important new treatment opportunities.