Second Messenger Systems in Alzheimer's Disease: A Quantitative Autoradiographic Study

Quantitative ligand binding autoradiography was used to map key components of second messenger systems in the CNS. [3H]-Forskolin binding to Gs-adenylate cyclase and [3H]-phorbol 12,13 dibutyrate (PDBu) binding to protein kinase C was investigated in human postmortem brain of control patients and patients with Alzheimer's Disease (AD). Disruption of glutamatergic and cholinergic systems may contribute to the pathology of AD. In view of this, alterations in ligand binding sites following selective lesions of glutamatergic and cholinergic pathways in rat brain were used as a framework on which to elucidate possible plastic modifications of second messenger systems in AD. Since the primary lesion in AD occurs within the cortex, ligand binding to second messenger systems was investigated following excitotoxic lesion of the rat cerebral cortex. Second Messenger Ligand Binding in Alzheimer's Disease:In two separate series, [3H]-forskolin binding was investigated in a total of 15 controls and 16 age-matched patients dying with AD in middle frontal and temporal cortices and in the hippocampal formation. AD brains contained numerous neuritic plaques in both cortical areas and the hippocampal region, whilst controls had minimal neuritic plaques. Choline acetyltransferase (ChAT) activity was significantly reduced (>50%) in AD compared to control subjects in both cortex and the hippocampus. [3H]-Forskolin binding was significantly reduced by approximately 50% in all layers of the middle frontal cortex in AD brain compared to controls. There was a positive correlation between [3H]-forskolin binding and ChAT activity in each layer of frontal cortex (correlation coefficient, r = 0.662 - 0.712) when data from control and AD brain were combined. [3H]-Forskolin binding was minimally altered in 1 of the 11 discrete regions examined in the hippocampus in AD brain compared to control. ChAT activity and [3H]-forskolin binding were unrelated in any region of the hippocampus (r = 0.42 - 0.6). In the temporal cortex and the molecular layer of the dentate gyrus, there was evidence that [3 H]-forskolin binding was lower in AD patients compared to control subjects. Whether these changes achieved the probability level of 5% was a reflection of group size, variability of measurements, and the errors of sampling heterogeneous populations. There was no association between the number of neuritic plaques and [3H]-forskolin binding in any brain region examined. The effect of 5'guanylimidodiphosphate (Gpp(NH)p) on [3H]-forskolin binding was examined in adjacent sections from the same group of control and AD patients. In control brain, basal levels of [3H]-forskolin binding were significantly increased in layers I-III of middle frontal cortex (28%) and middle temporal cortex (30%) in the presence of Gpp(NH)p. In AD brain, the ability of Gpp(NH)p to enhance [3H]-forskolin binding from basal levels in cortical layers (I-III) was conserved. Gpp(NH)p had no effect on the level of [3H]-forskolin binding within each region of the hippocampus in the control or AD group. In a separate study, both quantitative autoradiography and homogenate binding to particulate and cytosolic fractions were employed to investigate [3H]-PDBu binding in middle frontal and temporal cortices, and the hippocampal region of nine control and nine AD subjects. All AD brains exhibited extensive signs of the pathology classically associated with the disease, namely numerous neuritic plaques and a profound reduction in ChAT activity ( 60%) in both cortical areas and the hippocampus. Quantitative autoradiographic analysis of [3H]-PDBu binding showed there was no significant difference between control and AD sections in all areas examined within the middle frontal and temporal cortices and hippocampal formation. In adjacent sections to those used for [3H]-PDBu autoradiography, [3H]-forskolin binding was markedly reduced in all layers of middle frontal and temporal cortex (at least 30%) and in the molecular layer of the dentate gyrus (38%) in AD when compared with control subjects. In a parallel study, [3H]-PDBu binding to homogenate preparations of control and AD brain confirmed that there was no significant difference in [3H]-PDBu binding in either the particulate or cytosolic fraction. (Abstract shortened by ProQuest.)

Angiotensin II-inhibition:effect on Alzheimer's pathology in the aged triple transgenic mouse

Reducing excessive accumulation of amyloid-β (Aβ) in Alzheimer's disease (AD) is a key objective of most AD therapies, and inhibition of angiotensin-converting enzyme (ACE) may delay onset or progression of AD. The effects of an ACE-inhibitor (ACE-I) and an angiotensin II receptor blocker (ARB) on Aβ and tau pathology in a triple transgenic (3xTGAD) mouse model of AD were investigated. 9-10month 3xTGAD mice were treated with ARB, ACE-I or vehicle for 6 months. Mean arterial blood pressure (MABP) was measured periodically and mice were assessed behaviourally. Aβ, phospho-tau, amyloid precursor protein (APP) and ACE activity were analysed. MABP was significantly reduced at 2 weeks and 3 months in the ACE-I group and at 3 months in the ARB group, compared to vehicle. Neither drug altered performance of 3xTGAD mice in Morris Water Maze or T-maze, nor were Aβ, tau immunolabelling or APP levels altered. ACE-I significantly reduced ACE activity in kidney. Prolonged treatment with ACE-I or ARB does not affect Aβ or phospho-tau accumulation in brains of aged 3xTGAD mice

The Subtype of GluN2 C-terminal Domain Determines the Response to Excitotoxic Insults

It is currently unclear whether the GluN2 subtype influences NMDA receptor (NMDAR) excitotoxicity. We report that the toxicity of NMDAR-mediated Ca(2+) influx is differentially controlled by the cytoplasmic C-terminal domains of GluN2B (CTD(2B)) and GluN2A (CTD(2A)). Studying the effects of acute expression of GluN2A/2B-based chimeric subunits with reciprocal exchanges of their CTDs revealed that CTD(2B) enhances NMDAR toxicity, compared to CTD(2A). Furthermore, the vulnerability of forebrain neurons in vitro and in vivo to NMDAR-dependent Ca(2+) influx is lowered by replacing the CTD of GluN2B with that of GluN2A by targeted exon exchange in a mouse knockin model. Mechanistically, CTD(2B) exhibits stronger physical/functional coupling to the PSD-95-nNOS pathway, which suppresses protective CREB activation. Dependence of NMDAR excitotoxicity on the GluN2 CTD subtype can be overcome by inducing high levels of NMDAR activity. Thus, the identity (2A versus 2B) of the GluN2 CTD controls the toxicity dose-response to episodes of NMDAR activity

Impaired Glymphatic Function and Pulsation Alterations in a Mouse Model of Vascular Cognitive Impairment

ACKNOWLEDGMENTS Schematic diagrams in Figures 2, 8 are created withBiorender.com. FUNDING We gratefully acknowledge the grant support from the Alzheimer’s Society (152 (PG-157); 290 (AS-PG-15b-018); 228 (AS-DTC-2014-017), 314 (AS –PhD-16-006), and Alzheimer’s Research United Kingdom (ART-PG2010-3; ARUK-PG2013- 22; ARUK-PG2016B-6), and The University of Edinburgh Centre for Cognitive Ageing and Cognitive Epidemiology, part of the cross council Lifelong Health and Wellbeing Initiative (G0700704/84698). ML and JB are funded by an Alzheimer’s Society Scotland Doctoral Training Programme and RS Macdonald Trust. ML was also funded by a China Scholarship Council (CSC)/University of Edinburgh scholarship.Peer reviewedPublisher PD

Minimal muscle damage after a marathon and no influence of beetroot juice on inflammation and recovery

This study examined whether beetroot juice (BTJ) would attenuate inflammation and muscle damage following a marathon. Using a double blind, independent group’s design, 34 runners (~16 previous marathons completed) consumed either BTJ or an isocaloric placebo (PLA) for 3 days following a marathon. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), muscle soreness, serum cytokines, leucocytosis, creatine kinase (CK), high sensitivity C-reactive protein (hs-CRP) and aspartate aminotransferase (AST) were measured pre, post, and on the 2 days after the marathon. CMJ and MIVC were reduced after the marathon (P0.05). Muscle soreness was increased in the day after the marathon (BTJ; 45±48 vs. PLA; 46±39 mm) and had returned to baseline by day 2, irrespective of supplementation (P=0.694). Cytokines (Interleukin-6; IL-6, interleukin-8, tumour necrosis factor-α) were increased immediately post-marathon but apart from IL-6 had returned to baseline values by day 1 post. No interaction effects were evident for IL-6 (P=0.213). Leucocytes increased 1.7 fold after the race and remained elevated 2 days post, irrespective of supplement (P<0.0001). CK peaked at 1 day post marathon (BTJ: 965±967 & PLA: 1141±979 IU·L-1) and like AST and hs-CRP, was still elevated 2 days after the marathon (P<0.05); however, no group differences were present for these variables. Beetroot juice did not attenuate inflammation or reduce muscle damage following a marathon, possibly because most of these indices were not markedly different from baseline values in the days after the marathon

Engaging with community researchers for exposure science: lessons learned from a pesticide biomonitoring study

A major challenge in biomonitoring studies with members of the general public is ensuring their continued involvement throughout the necessary length of the research. The paper presents evidence on the use of community researchers, recruited from local study areas, as a mechanism for ensuring effective recruitment and retention of farmer and resident participants for a pesticides biomonitoring study. The evidence presented suggests that community researchers' abilities to build and sustain trusting relationships with participants enhanced the rigour of the study as a result of their on-the-ground responsiveness and flexibility resulting in data collection beyond targets expected

Recent progress in translational research on neurovascular and neurodegenerative disorders

The already established and widely used intravenous application of recombinant tissue plasminogen activator as a re-opening strategy for acute vessel occlusion in ischemic stroke was recently added by mechanical thrombectomy, representing a fundamental progress in evidence-based medicine to improve the patient’s outcome. This has been paralleled by a swift increase in our understanding of pathomechanisms underlying many neurovascular diseases and most prevalent forms of dementia. Taken together, these current advances offer the potential to overcome almost two decades of marginally successful translational research on stroke and dementia, thereby spurring the entire field of translational neuroscience. Moreover, they may also pave the way for the renaissance of classical neuroprotective paradigms. This review reports and summarizes some of the most interesting and promising recent achievements in neurovascular and dementia research. It highlights sessions from the 9th International Symposium on Neuroprotection and Neurorepair that have been discussed from April 19th to 22nd in Leipzig, Germany. To acknowledge the emerging culture of interdisciplinary collaboration and research, special emphasis is given on translational stories ranging from fundamental research on neurode- and -regeneration to late stage translational or early stage clinical investigations

Microglia regulate myelin growth and integrity in the central nervous system

Myelin is required for the function of neuronal axons in the central nervous system, but the mechanisms that support myelin health are unclear. Although macrophages in the central nervous system have been implicated in myelin health(1), it is unknown which macrophage populations are involved and which aspects they influence. Here we show that resident microglia are crucial for the maintenance of myelin health in adulthood in both mice and humans. We demonstrate that microglia are dispensable for developmental myelin ensheathment. However, they are required for subsequent regulation of myelin growth and associated cognitive function, and for preservation of myelin integrity by preventing its degeneration. We show that loss of myelin health due to the absence of microglia is associated with the appearance of a myelinating oligodendrocyte state with altered lipid metabolism. Moreover, this mechanism is regulated through disruption of the TGFβ1–TGFβR1 axis. Our findings highlight microglia as promising therapeutic targets for conditions in which myelin growth and integrity are dysregulated, such as in ageing and neurodegenerative disease(2,3)