Neuropathology and cholinesterase expression in the brains of octogenarians and older.

A subset of octogenarians and older maintain normal cognitive function (CNOO) despite high prevalence and incidence of cognitive decline attributed to neurodegeneration or aging in the population. The rostral prefrontal cortex (rPFC) and hippocampal formation are brain regions integral to cognition, namely attention and memory, facilitated in part by cholinergic innervation. We hypothesized that preserved cholinergic neurotransmission in these regions contributes to intact cognition in the CNOO. To test this, we evaluated the burden of neuropathological and cholinesterase-associated protein aggregates in the rPFC and hippocampal formation. Tissues from age- and sex-matched CNOO and Alzheimer's disease (AD) rPFC and hippocampal formation were stained for ß-amyloid (Aß), tau, α-synuclein, phosphorylated TAR DNA-binding protein 43 (pTDP-43), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). The relative abundance of neuropathological aggregates was semi-quantitatively scored. Deposition of Aß plaques, tau neurofibrillary tangles (NFT) and pTDP-43 inclusions were comparable between CNOO and AD cases. Intraneuronal Aß and tau-positive thorny astrocytes consistent with aging-related tau astrogliopathy, were also noted in the rPFC. Abundance of BChE-positive plaque pathology was significantly higher in AD than in CNOO cases in most regions of interest, followed closely by abundance of AChE-positive plaque pathology. BChE and AChE activities were also associated with varied NFT morphologies. CNOO cases maintained cognition despite a high neuropathological burden in the rPFC and hippocampal formation. BChE-positive and, to a lesser extent, AChE-positive pathologies were significantly lower in most regions in the CNOO compared to AD. This suggests a specificity of cholinesterase-associated neuropathology with AD. We conclude that while CNOO have cholinesterase-associated neuropathology in the rPFC and hippocampal formation, abundance in this population is significantly lower compared to AD which may contribute to their intact cognition.

Clinicopathological correlations and cholinesterase expression in early-onset familial Alzheimer's disease with the presenilin 1 mutation, Leu235Pro.

In sporadic Alzheimer's disease (SpAD), acetylcholinesterase and butyrylcholinesterase, co-regulators of acetylcholine, are associated with ß-amyloid plaques and tau neurofibrillary tangles in patterns suggesting a contribution to neurotoxicity. This association has not been explored in early-onset familial Alzheimer's disease (FAD). We investigated whether cholinesterases are observed in the neuropathological hallmarks in FAD expressing the presenilin 1 Leu235Pro mutation. Brain tissues from three FAD cases and one early-onset SpAD case were stained and analyzed for ß-amyloid, tau, α-synuclein, acetylcholinesterase and butyrylcholinesterase. AD pathology was prominent throughout the rostrocaudal extent of all 4 brains but α-synuclein-positive neurites were present in only one familial case. In FAD and SpAD cases, cholinergic activity was associated with plaques and tangles but not with α-synuclein pathology. Both cholinesterases showed similar or decreased plaque staining than detected with ß-amyloid immunostaining but greater plaque deposition than observed with thioflavin-S histofluorescence. Acetylcholinesterase and butyrylcholinesterase are highly associated with AD pathology in inherited disease and both may represent specific diagnostic and therapeutic targets for all AD forms.

Clinical and neuropathological variability in the rare IVS10 + 14 tau mutation.

Mutations in the microtubule-associated protein tau gene are known to cause progressive neurodegenerative disorders with variable clinical and neuropathological phenotypes, including the intronic 10 + 14 (IVS10 + 14) splice site mutation. Three families have been reported with the IVS10 + 14 microtubule-associated protein tau mutation. Here, we describe the clinical and neuropathological data from an additional family. Neuropathological data were available for 2 of the 3 cases, III-4, and III-5. While III-5 had widespread tau deposition and atrophy, III-4 exhibited more mild neuropathological changes except for the substantia nigra. The previously reported families that express the IVS10 + 14 mutation exhibited significant interfamilial heterogeneity, with symptoms including amyotrophy, dementia, disinhibition, parkinsonism, and breathing problems. In addition to expressing many of these symptoms, members of this fourth family experienced profound sensory abnormalities and sleep disturbance. Although there were probable clinicopathological correlates for the symptoms expressed by the earlier families and III-5 from our cohort, pathology in III-4 did not appear sufficient to explain symptom severity. This indicates the need to explore alternate mechanisms of tau-induced brain dysfunction.

2-Pyridone natural products as inhibitors of SARS-CoV-2 main protease.

The disease, COVID-19, is caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2) for which there is currently no treatment. The SARS-CoV-2 main protease (Mpro) is an important enzyme for viral replication. Small molecules that inhibit this protease could lead to an effective COVID-19 treatment. The 2-pyridone scaffold was previously identified as a possible key pharmacophore to inhibit SARS-CoV-2 Mpro. A search for natural, antimicrobial products with the 2-pyridone moiety was undertaken herein, and their calculated potency as inhibitors of SARS-CoV-2 Mpro was investigated. Thirty-three natural products containing the 2-pyridone scaffold were identified from the literature. An in silico methodology using AutoDock was employed to predict the binding energies and inhibition constants (Ki values) for each 2-pyridone-containing compound with SARS-CoV-2 Mpro. This consisted of molecular optimization of the 2-pyridone compound, docking of the compound with a crystal structure of SARS-CoV-2 Mpro, and evaluation of the predicted interactions and ligand-enzyme conformations. All compounds investigated bound to the active site of SARS-CoV-2 Mpro, close to the catalytic dyad (His-41 and Cys-145). Thirteen molecules had predicted Ki values <1 µM. Glu-166 formed a key hydrogen bond in the majority of the predicted complexes, while Met-165 had some involvement in the complex binding as a close contact to the ligand. Prominent 2-pyridone compounds were further evaluated for their ADMET properties. This work has identified 2-pyridone natural products with calculated potent inhibitory activity against SARS-CoV-2 Mpro and with desirable drug-like properties, which may lead to the rapid discovery of a treatment for COVID-19.

Quantification of Butyrylcholinesterase Activity as a Sensitive and Specific Biomarker of Alzheimer's Disease.

Amyloid-ß (Aß) plaques are a neuropathological hallmark of Alzheimer's disease (AD); however, a significant number of cognitively normal older adults can also have Aß plaques. Thus, distinguishing AD from cognitively normal individuals with Aß plaques (NwAß) based on Aß plaque detection is challenging. It has been observed that butyrylcholinesterase (BChE) accumulates in plaques preferentially in AD. Thus, detecting BChE-associated plaques has the potential as an improved AD biomarker. We present Aß, thioflavin-S, and BChE quantification of 26 postmortem brain tissues; AD (n = 8), NwAß (n = 6), cognitively normal without plaques (n = 8), and other common dementias including corticobasal degeneration, frontotemporal dementia with tau, dementia with Lewy bodies, and vascular dementia. Pathology burden in the orbitofrontal cortex, entorhinal cortex, amygdala, and hippocampal formation was determined and compared. The predictive value of Aß and BChE quantification was determined, via receiver-operating characteristic plots, to evaluate their AD diagnostic performance using sensitivity, specificity, and area under curve (AUC) metrics. In general, Aß and BChE-associated pathology were greater in AD, particularly in the orbitofrontal cortex. In this region, the largest increase (9.3-fold) was in BChE-associated pathology, observed between NwAß and AD, due to the virtual absence of BChE-associated plaques in NwAß brains. Furthermore, BChE did not associate with pathology of the other dementias. In this sample, BChE-associated pathology provided better diagnostic performance (AUC = 1.0, sensitivity/specificity = 100% /100%) when compared to Aß (AUC = 0.98, 100% /85.7%). These findings highlight the predictive value of BChE as a biomarker for AD that could facilitate timely disease diagnosis and management.

Butyrylcholinesterase is associated with ß-amyloid plaques in the transgenic APPSWE/PSEN1dE9 mouse model of Alzheimer disease.

Histochemical analysis of Alzheimer disease (AD) brain tissues indicates that butyrylcholinesterase (BuChE) is present in ß-amyloid (Aß) plaques. The role of BuChE in AD pathology is unknown, but an animal model developing similar BuChE-associated Aß plaques could provide insights. The APPSWE/PSEN1dE9 transgenic mouse (ADTg), which develops Aß plaques, was examined to determine if BuChE associates with these plaques, as in AD. We found that in mature ADTg mice, BuChE activity associated with Aß plaques. The Aß-, thioflavin-S- and BuChE-positive plaques mainly accumulated in the olfactory structures, cerebral cortex, hippocampal formation, amygdala, and cerebellum. No plaques were stained for acetylcholinesterase activity. The distribution and abundance of plaque staining in ADTg closely resembled many aspects of plaque staining in AD. Butyrylcholinesterase staining consistently showed fewer plaques than were detected with Aß immunostaining but a greater number of plaques than were visualized with thioflavin-S. Double-labeling experiments demonstrated that all BuChE-positive plaques were Aß positive, whereas only some BuChE-positive plaques were thioflavin-S positive. These observations suggest that BuChE is associated with a subpopulation of Aß plaques and may play a role in AD plaque maturation. A further study of this animal model could clarify the role of BuChE in AD pathology.