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ABSTRACT The French composer, Maurice Ravel, at the peak of his career, showed signs of a progressive disorder that affected his ability to function with verbal and musical language, as noted by the neurologist Théophile Alajouanine. The worsening of the disease led to a craniotomy, performed in 1937, which failed to reveal the cause of his illness, and he died shortly thereafter. A lack of post-mortem neuropathological evidence precluded a definitive diagnosis of the illness, which remained enigmatic. Speculations about the precise diagnosis of Ravel's neurological disease have been largely based on Alajouanine's observations, which included aphasia and amusia, mostly expressive, and ideomotor apraxia, while musical judgement, taste, and memory remained relatively intact, implying different neuroanatomical substrates. A possible subform of frontotemporal lobar degeneration complex was the diagnostic suggestion of many authors. His untimely death deprived the world of this remarkable musician, and the music that remained trapped in his mind.

Cholinesterase (ChE) enzymes have been identified as diagnostic markers for Alzheimer disease (AD). Substrate-based probes have been synthesised to detect ChEs but they have not detected changes in ChE distribution associated with AD pathology. Probes are typically screened using spectrophotometric methods with pure enzyme for specificity and kinetics. However, the biochemical properties of ChEs associated with AD pathology are altered. The present work was undertaken to determine whether the Karnovsky-Roots (KR) histochemical method could be used to evaluate probes at the site of pathology. Thirty thioesters and esters were synthesised and evaluated using enzyme kinetic and KR methods. Spectrophotometric methods demonstrated all thioesters were ChE substrates, yet only a few provided staining in the brain with the KR method. Esters were ChE substrates with interactions with brain ChEs. These results suggest that the KR method may provide an efficient means to screen compounds as probes for imaging AD-associated ChEs.

Abstract Neuroimaging with [2,2-dimethyl-3-[(2R,3E)-3-oxidoiminobutan-2-yl]azanidylpropyl]-[(2R,3E)-3-hydroxyiminobutan-2-yl]azanide;oxo(99Tc)technetium-99(3+) ([99mTc]HMPAO) single photon emission computed tomography (SPECT) is used in Alzheimer’s disease (AD) to evaluate regional cerebral blood flow (rCBF). Hypoperfusion in select temporoparietal regions has been observed in human AD. However, it is unknown whether AD hypoperfusion signatures are also present in the 5XFAD mouse model. The current study was undertaken to compare baseline brain perfusion between 5XFAD and wild-type (WT) mice using [99mTc]HMPAO SPECT and determine whether hypoperfusion is recapitulated in 5XFAD mice. 5XFAD and WT mice underwent a 45 min SPECT scan, 20 min after [99mTc]HMPAO administration. Whole brain and regional standardized uptake values (SUV) and regional relative standardized uptake values (SUVR) with whole brain reference were compared between groups. Brain perfusion was similar between WT and 5XFAD brains. Whole brain [99mTc]HMPAO retention revealed no significant difference in SUV (5XFAD, 0.372 ± 0.762; WT, 0.640 ± 0.955; p = 0.536). Similarly, regional analysis revealed no significant differences in [99mTc]HMPAO metrics between groups (SUV: 0.357 ≤ p ≤ 0.640; SUVR: 0.595 ≤ p ≤ 0.936). These results suggest apparent discrepancies in rCBF between human AD and the 5XFAD model. Establishing baseline perfusion patterns in 5XFAD mice is essential to inform pre-clinical diagnostic and therapeutic drug discovery programs.

Abstract Introduction Alzheimer's disease (AD) is characterized by neurotoxic immuno‐inflammation concomitant with cytotoxic oligomerization of amyloid beta (Aβ) and tau, culminating in concurrent, interdependent immunopathic and proteopathic pathogeneses. Methods We performed a comprehensive series of in silico, in vitro, and in vivo studies explicitly evaluating the atomistic–molecular mechanisms of cytokine‐mediated and Aβ‐mediated neurotoxicities in AD. Next, 471 new chemical entities were designed and synthesized to probe the pathways identified by these molecular mechanism studies and to provide prototypic starting points in the development of small‐molecule therapeutics for AD. Results In response to various stimuli (e.g., infection, trauma, ischemia, air pollution, depression), Aβ is released as an early responder immunopeptide triggering an innate immunity cascade in which Aβ exhibits both immunomodulatory and antimicrobial properties (whether bacteria are present, or not), resulting in a misdirected attack upon “self” neurons, arising from analogous electronegative surface topologies between neurons and bacteria, and rendering them similarly susceptible to membrane‐penetrating attack by antimicrobial peptides (AMPs) such as Aβ. After this self‐attack, the resulting necrotic (but not apoptotic) neuronal breakdown products diffuse to adjacent neurons eliciting further release of Aβ, leading to a chronic self‐perpetuating autoimmune cycle. AD thus emerges as a brain‐centric autoimmune disorder of innate immunity. Based upon the hypothesis that autoimmune processes are susceptible to endogenous regulatory processes, a subsequent comprehensive screening program of 1137 small molecules normally present in human brain identified tryptophan metabolism as a regulator of brain innate immunity and a source of potential endogenous anti‐AD molecules capable of chemical modification into multi‐site therapeutic modulators targeting AD's complex immunopathic–proteopathic pathogenesis. Discussion Conceptualizing AD as an autoimmune disease, identifying endogenous regulators of this autoimmunity, and designing small molecule drug‐like analogues of these endogenous regulators represents a novel therapeutic approach for AD.

Upon publication of this article [1], it was brought to our attention that one of the 303 participants in the normative study should have been deleted from the database.

Sections from the middle frontal gyrus (Brodmann area 46) of autopsy-confirmed Alzheimer’s disease (AD) patients and non-demented subjects were examined for the prevalence of hallmark AD pathology, including amyloid-β (Aβ) plaques, phosphorylated tau (pTau) tangles, neuroinflammation and synaptic loss (n = 7 subjects/group). Dense-core deposits of Aβ were present in all AD patients (7/7) and some non-demented subjects (3/7), as evidenced by 6E10 immunohistochemistry. Levels of Aβ immunoreactivity were higher in AD vs. non-AD cases. For pTau, AT8-positive neurofibrillary tangles and threads were exclusively observed in AD patient tissue. Levels of [3H]PK11195 binding to the translocator protein (TSPO), a marker of inflammatory processes, were elevated in the gray matter of AD patients compared to non-demented subjects. Levels of [3H]UCB-J binding to synaptic vesicle glycoprotein 2A (SV2A), a marker of synaptic density, were not different between groups. In AD patients, pTau immunoreactivity was positively correlated with [3H]PK11195, and negatively correlated with [3H]UCB-J binding levels. No correlation was observed between Aβ immunoreactivity and markers of neuroinflammation or synaptic density. These data demonstrate a close interplay between tau pathology, inflammation and SV2A density in AD, and provide useful information on the ability of neuroimaging biomarkers to diagnose AD dementia.

Abstract Background A need exists for easily administered assessment tools to detect mild cognitive changes that are more comprehensive than screening tests but shorter than a neuropsychological battery and that can be administered by physicians, as well as any health care professional or trained assistant in any medical setting. The Toronto Cognitive Assessment (TorCA) was developed to achieve these goals. Methods We obtained normative data on the TorCA (n = 303), determined test reliability, developed an iPad version, and validated the TorCA against neuropsychological assessment for detecting amnestic mild cognitive impairment (aMCI) (n = 50/57, aMCI/normal cognition). For the normative study, healthy volunteers were recruited from the Rotman Research Institute registry. For the validation study, the sample was comprised of participants with aMCI or normal cognition based on neuropsychological assessment. Cognitively normal participants were recruited from both healthy volunteers in the normative study sample and the community. Results The TorCA provides a stable assessment of multiple cognitive domains. The total score correctly classified 79% of participants (sensitivity 80%; specificity 79%). In an exploratory logistic regression analysis, indices of Immediate Verbal Recall, Delayed Verbal and Visual Recall, Visuospatial Function, and Working Memory/Attention/Executive Control, a subset of the domains assessed by the TorCA, correctly classified 92% of participants (sensitivity 92%; specificity 91%). Paper and iPad version scores were equivalent. Conclusions The TorCA can improve resource utilization by identifying patients with aMCI who may not require more resource-intensive neuropsychological assessment. Future studies will focus on cross-validating the TorCA for aMCI, and validation for disorders other than aMCI.

Neuroinflammation, characterized by chronic activation of the myeloid-derived microglia, is a hallmark of Alzheimer’s disease (AD). Systemic inflammation, typically resulting from infection, has been linked to the progression of AD due to exacerbation of the chronic microglial reaction. However, the mechanism and the consequences of this exacerbation are largely unknown. Here, we mimicked systemic inflammation in AD with weekly intraperitoneal (i.p.) injections of APPSWE/PS1ΔE9 transgenic mice with E. coli lipopolysaccharide (LPS) from 9 to 12 months of age, corresponding to the period with the steepest increase in amyloid pathology. We found that the repeated LPS injections ameliorated amyloid pathology in the neocortex while increasing the neuroinflammatory reaction. To elucidate mechanisms, we analyzed the proteome of the hippocampus from the same mice as well as in unique samples of CNS myeloid cells. The repeated LPS injections stimulated protein pathways of the complement system, retinoid receptor activation and oxidative stress. CNS myeloid cells from transgenic mice showed enrichment in pathways of amyloid-beta clearance and elevated levels of the lysosomal protease cathepsin Z, as well as amyloid precursor protein, apolipoprotein E and clusterin. These proteins were found elevated in the proteome of both LPS and vehicle injected transgenics, and co-localized to CD11b+ microglia in transgenic mice and in primary murine microglia. Additionally, cathepsin Z, amyloid precursor protein, and apolipoprotein E appeared associated with amyloid plaques in neocortex of AD cases. Interestingly, cathepsin Z was expressed in microglial-like cells and co-localized to CD68+ microglial lysosomes in AD cases, and it was expressed in perivascular cells in AD and control cases. Taken together, our results implicate systemic LPS administration in ameliorating amyloid pathology in early-to-mid stage disease in the APPSWE/PS1ΔE9 mouse and attract attention to the potential disease involvement of cathepsin Z expressed in CNS myeloid cells in AD.

Kinetic studies and molecular modeling of human acetylcholinesterase (AChE) inhibition by a fluorinated acetophenone derivative, 1-(3-tert-butylphenyl)-2,2,2-trifluoroethanone (TFK), were performed. Fast reversible inhibition of AChE by TFK is of competitive type with Ki = 5.15 nM. However, steady state of inhibition is reached slowly. Kinetic analysis showed that TFK is a slow-binding inhibitor (SBI) of type B with Ki* = 0.53 nM. Reversible binding of TFK provides a long residence time, τ = 20 min, on AChE. After binding, TFK acylates the active serine, forming an hemiketal. Then, disruption of hemiketal (deacylation) is slow. AChE recovers full activity in approximately 40 min. Molecular docking and MD simulations depicted the different steps. It was shown that TFK binds first to the peripheral anionic site. Then, subsequent slow induced-fit step enlarged the gorge, allowing tight adjustment into the catalytic active site. Modeling of interactions between TFK and AChE active site by QM/MM showed that the “isomerization” step of enzyme-inhibitor complex leads to a complex similar to substrate tetrahedral intermediate, a so-called “transition state analog”, followed by a labile covalent intermediate. SBIs of AChE show prolonged pharmacological efficacy. Thus, this fluoroalkylketone intended for neuroimaging, could be of interest in palliative therapy of Alzheimer’s disease and protection of central AChE against organophosphorus compounds.

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) hydrolyze the neurotransmitter acetylcholine and, thereby, function as coregulators of cholinergic neurotransmission. Although closely related, these enzymes display very different substrate specificities that only partially overlap. This disparity is largely due to differences in the number of aromatic residues lining the active site gorge, which leads to large differences in the shape of the gorge and potentially to distinct interactions with an individual ligand. Considerable structural information is available for the binding of a wide diversity of ligands to AChE. In contrast, structural data on the binding of reversible ligands to BChE are lacking. In a recent effort, an inhibitor competition approach was used to probe the overlap of ligand binding sites in BChE. Here, we extend this study by solving the crystal structures of human BChE in complex with five reversible ligands, namely, decamethonium, thioflavin T, propidium, huprine, and ethopropazine. We compare these structures to equivalent AChE complexes when available in the protein data bank and supplement this comparison with kinetic data and observations from isothermal titration calorimetry. This new information now allows us to define the binding mode of various ligand families and will be of importance in designing specific reversible ligands of BChE that behave as inhibitors or reactivators.

Most carbamates are pseudoirreversible inhibitors of cholinesterases. Phenothiazine carbamates exhibit this inhibition of acetylcholinesterase but produce reversible inhibition of butyrylcholinesterase, suggesting that they do not form a covalent bond with the catalytic serine. This atypical inhibition is attributable to π−π interaction of the phenothiazine moiety with F329 and Y332 in butyrylcholinesterase. These residues are in a helical segment, referred to here as the E-helix because it contains E325 of the catalytic triad. The involvement of the E-helix in phenothiazine carbamate reversible inhibition of butyrylcholinesterase is confirmed using mutants of this enzyme at A328, F329, or Y332 that show typical pseudoirreversible inhibition. Thus, in addition to various domains of the butyrylcholinesterase active site gorge, such as the peripheral anionic site and the π-cationic site of the Ω-loop, the E-helix represents a domain that could be exploited for development of specific inhibitors to treat dementias. [ABSTRACT FROM AUTHOR]

It has been hypothesized that acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) are coregulators of the duration of action of acetylcholine in cholinergic neurotransmission, suggesting that BuChE may also have an important role in the brain. To compare the expression of cholinesterases in the human thalamus, the distributions of BuChE and AChE activity were studied by using a modified Karnovsky-Roots method. BuChE activity was present mainly in neurons, whereas AChE activity was present in both neurons and axons. There was intense staining for BuChE or AChE throughout the thalamus, with some nuclei primarily expressing one or the other cholinesterase. BuChE staining was most intense and widespread in neurons in the anteroventral, mediodorsal, ventral, lateral, and pulvinar thalamic nuclei. AChE was predominantly expressed in neurons of the anterodorsal, midline, ventral, intralaminar, and reticular nuclei. Many nuclei contained both cholinesterases. Considering the overall patterns of labeling in the thalamus for the two cholinesterases, there were both complementary and overlapping relationships of BuChE and AChE activity. Neuronal staining in the subthalamic nucleus and hypothalamus was predominantly positive for AChE activity. The distinct distribution of BuChE activity in neurons in the human thalamus is consistent with an important role for this enzyme in neurotransmission in the human nervous system. Furthermore, BuChE activity, like AChE activity, is found in certain thalamic nuclei related to cognitive and behavioral functions. Involvement of thalamic nuclei in diseases of the nervous system such as Alzheimer's disease and schizophrenia suggests that BuChE could be a potential target for therapeutic intervention in these disorders. J. Comp. Neurol. 463:25–43, 2003. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Current approaches to the treatment of cognitive and behavioral symptoms of Alzheimer disease emphasize the use of cholinesterase inhibitors. The kinetic effects of the cholinesterase inhibitors donepezil, galantamine, metrifonate, physostigmine, rivastigmine, and tetrahydroaminoacridine were examined with respect to their action on the esterase and aryl acylamidase activities of human acetylcholinesterase (AChE) and human butyrylcholinesterase (BuChE). Each of these drugs inhibited both AChE and BuChE, but to different degrees. Inhibition of BuChE by these compounds was approximately the same, or better, when acetylthiocholine, the analog of the neurotransmitter acetylcholine, was used as the substrate, instead of butyrylthiocholine. In addition, for these drugs, the inhibition of aryl acylamidase activity paralleled that observed for inhibition of esterase activity of AChE and BuChE. Given that drugs that are currently in use for the treatment of Alzheimer disease inhibit both AChE and BuChE, the development of drugs targeted toward the exclusive inhibition of one or the other cholinesterase may be important for understanding the relative importance of inhibition of BuChE and AChE in the treatment of this disease. [ABSTRACT FROM AUTHOR]