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Background: In Alzheimer’s disease (AD), and amyloid models such as the 5XFAD mouse, butyrylcholinesterase (BChE) is associated with β-amyloid (Aβ) plaques and has unique biochemical features which distinguish it from that found in neurons. It has been suggested that BChE associated with Aβ plaques may be involved in the maturation of this structure and thus disease progression. Objective: Currently, it is unknown whether BChE bound to Aβ plaques has altered biochemical properties due to a different primary structure or because of the association of this enzyme with Aβ plaques. Also, the source and binding mechanism of this BChE remains unknown. Methods: Brain tissue sections from the 5XFAD/BChE-KO mouse were incubated with exogenous sources of BChE and stained for this enzyme’s activity. Efforts were made to determine what region of BChE or Aβ may be involved in this association. Results: We found that incubation of 5XFAD/BChE-KO brain tissues with exogenous BChE led to this enzyme becoming associated with Aβ plaques and neurons. In contrast to neuronal BChE, the BChE bound to Aβ plaques had similar biochemical properties to those seen in AD. Mutations to BChE and efforts to block Aβ epitomes failed to prevent this association. Conclusion: The association of BChE with Aβ plaques, and the resultant biochemical changes, suggests that BChE may undergo a conformational change when bound to Aβ plaques but not neurons. The 5XFAD/BChE-KO model is ideally suited to explore the binding mechanism of BChE to Aβ plaques as well as the involvement of BChE in AD pathogenesis.

Molecular imaging agents targeting butyrylcholinesterase (BChE) have shown promise in other neurodegenerative disorders and may have utility in detecting changes to normal appearing white matter in multiple sclerosis (MS). BChE activity is present in white matter and localizes to activated microglia associated with MS lesions. The purpose of this study was to further characterize changes in the cholinergic system in MS pathology, and to explore the utility of BChE radioligands as potential diagnostic and treatment monitoring agents in MS. Cortical and white matter lesions were identified using myelin staining, and lesions were classified based on microglial activation patterns. Adjacent brain sections were used for cholinesterase histochemistry and in vitro autoradiography using phenyl 4-[123I]-iodophenylcarbamate (123I-PIP), a previously described small-molecule cholinesterase-binding radioligand. BChE activity is positively correlated with microglial activation in white matter MS lesions. There is no alteration in cholinesterase activity in cortical MS lesions. 123I-PIP autoradiography revealed uptake of radioactivity in normal white matter, absence of radioactivity within demyelinated MS lesions, and variable uptake of radioactivity in adjacent normal-appearing white matter. BChE imaging agents have the potential to detect MS lesions and subtle pathology in normal-appearing white matter in postmortem MS brain tissue. The possibility of BChE imaging agents serving to supplement current diagnostic and treatment monitoring strategies should be evaluated.

The cetacean hippocampal formation has been noted to be one of the smallest relative to brain size of all mammals studied. This region, comprised of the dentate gyrus, hippocampus proper, subiculum, presubiculum, parasubiculum and the entorhinal cortex, is important in learning, memory, and navigation. There have been a number of studies detailing the distribution of acetylcholinesterase (AChE) in the hippocampal formation of terrestrial mammals with the goal of gaining a greater understanding of some aspects of the cholinergic innervation to this region, as well as its parcellation. The present study was undertaken to describe the organization, cytoarchitecture, and distribution of AChE in the hippocampal formation of the Atlantic white-sided dolphin (AWSD) with the view to understand similarities and differences between this aquatic mammal and terrestrial mammals. Nissl-staining demonstrated cytoarchitecture of the hippocampal formation in the AWSD comparable to that reported in other cetaceans. In addition, the AWSD had a rich pattern of AChE staining that distinctly varied between regions and laminae. A number of differences in the distribution of AChE staining in areas comparable to those of terrestrial species reported suggested possible alterations in connectivity of this region. Overall, however, AChE-staining suggested that cholinergic innervation, neural pathways and function of the hippocampal formation of the AWSD is conserved, similar to other mammals.

The basal forebrain (BFB) cholinergic neurotransmitter system is important in a number of brain functions including attention, memory, and the sleep-wake cycle. The size of this region has been linked to the increase in encephalization of the brain in a number of species. Cetaceans, particularly those belonging to the family Delphinidae, have a relatively large brain compared to its body size and it is expected that the cholinergic BFB in the dolphin would be a prominent feature. However, this has not yet been explored in detail. This study examines and maps the neuroanatomy and cholinergic chemoarchitecture of the BFB in the Atlantic white-sided dolphin (Lagenorhynchus acutus). As in some other mammals, the BFB in this species is a prominent structure along the medioventral surface of the brain. The parcellation and distribution of cholinergic neural elements of the dolphin BFB was comparable to that observed in other mammals in that it has a medial septal nucleus, a nucleus of the vertical limb of the diagonal band of Broca, a nucleus of the horizontal limb of the diagonal band of Broca, and a nucleus basalis of Meynert. The observed BFB cholinergic system of this dolphin is consistent with evolutionarily conserved and important functions for survival.

Alzheimer's disease (AD) is the most common neurodegenerative disorder causing dementia. One hallmark of the AD brain is the deposition of β-amyloid (Aβ) plaques. AD is also a state of cholinergic dysfunction and butyrylcholinesterase (BChE) associates with Aβ pathology. A transgenic mouse (5XFAD) is an aggressive amyloidosis model, producing Aβ plaques with which BChE also associates. A derived strain (5XFAD/BChE-KO), with the BChE gene knocked out, has significantly lower fibrillar Aβ than 5XFAD mice at the same age. Therefore, BChE may have a role in Aβ pathogenesis. Furthermore, in AD, diminished glucose metabolism in the brain can be detected in vivo with positron emission tomography (PET) imaging following 2-deoxy-2-(18F)fluoro-D-glucose (18FDG) administration. To determine whether hypometabolism is related to BChE-induced changes in fibrillar Aβ burden, whole brain and regional uptake of 18FDG in 5XFAD and 5XFAD/BChE-KO mice was compared to corresponding wild-type (WT5XFAD and WTBChE-KO) strains at 5months. Diminished fibrillar Aβ burden was confirmed in 5XFAD/BChE-KO mice relative to 5XFAD. 5XFAD and 5XFAD/BChE-KO mice demonstrated reduction in whole brain 18FDG retention compared to respective wild-types. Regional analysis of relevant AD structures revealed reduction in 18FDG retention in 5XFAD mice in all brain regions analyzed (save cerebellum) compared to WT5XFAD. Alternatively, 5XFAD/BChE-KO mice demonstrated a more selective pattern of reduced retention in the cerebral cortex and thalamus compared to WTBChE-KO, while retention in hippocampal formation, amygdala and basal ganglia remained unchanged. This suggests that in knocking out BChE and reducing fibrillar Aβ, a possible protective effect on brain function may be conferred in a number of structures in 5XFAD/BChE-KO mice.

Amyloid-β (Aβ) plaques are a neuropathological hallmark of Alzheimer's disease (AD); however, a significant number of cognitively normal older adults can also have Aβ plaques. Thus, distinguishing AD from cognitively normal individuals with Aβ plaques (NwAβ) based on Aβ 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 Aβ, thioflavin-S, and BChE quantification of 26 postmortem brain tissues; AD (n = 8), NwAβ (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 Aβ 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, Aβ 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 NwAβ and AD, due to the virtual absence of BChE-associated plaques in NwAβ 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 Aβ (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.

Introduction Diagnosis of Alzheimer's disease (AD) in vivo, by molecular imaging of amyloid or tau, is constrained because similar changes can be found in brains of cognitively normal individuals. Butyrylcholinesterase (BChE), which becomes associated with these structures in AD, could elevate the accuracy of AD diagnosis by focusing on BChE pathology in the cerebral cortex, a region of scant BChE activity in healthy brain. Methods N-methylpiperidin-4-yl 4-[123I]iodobenzoate, a BChE radiotracer, was injected intravenously into B6SJL-Tg(APPSwFlLon, PSEN1∗M146 L∗L286 V) 6799Vas/Mmjax (5XFAD) mice and their wild-type (WT) counterparts for comparative single photon emission computed tomography (SPECT) studies. SPECT, computed tomography (CT), and magnetic resonance imaging (MRI) enabled comparison of whole brain and regional retention of the BChE radiotracer in both mouse strains. Results Retention of the BChE radiotracer was consistently higher in the 5XFAD mouse than in WT, and differences were particularly evident in the cerebral cortex. Discussion Cerebral cortical BChE imaging with SPECT can distinguish 5XFAD mouse model from the WT counterpart.

Brain glucose hypometabolism has been observed in Alzheimer’s disease (AD) patients, and is detected with 18 F radiolabelled glucose, using positron emission tomography. A pathological hallmark of AD is deposition of brain β - amyloid plaques that may influence cerebral glucose metabolism. The five times familial AD (5XFAD) mouse is a model of brain amyloidosis exhibiting AD-like phenotypes. This study examines brain β -amyloid plaque deposition and 18 FDG uptake, to search for an early biomarker distinguishing 5XFAD from wild-type mice. Thus, brain 18 FDG uptake and plaque deposition was studied in these mice at age 2, 5 and 13 months. The 5XFAD mice demonstrated significantly reduced brain 18 FDG uptake at 13 months relative to wild-type controls but not in younger mice, despite substantial β - amyloid plaque deposition. However, by comparing the ratio of uptake values for glucose in different regions in the same brain, 5XFAD mice could be distinguished from controls at age 2 months. This method of measuring altered glucose metabolism may represent an early biomarker for the progression of amyloid deposition in the brain. We conclude that brain 18 FDG uptake can be a sensitive biomarker for early detection of abnormal metabolism in the 5XFAD mouse when alternative relative uptake values are utilized.

Histochemical analysis of Alzheimer disease (AD) brain tissues indicates that butyrylcholinesterase (BuChE) is present in β-amyloid (Aβ) plaques. The role of BuChE in AD pathology is unknown, but an animal model developing similar BuChE-associated Aβ plaques could provide insights. The APPSWE/PSEN1dE9 transgenic mouse (ADTg), which develops Aβ 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 Aβ plaques. The Aβ-, 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 Aβ immunostaining but a greater number of plaques than were visualized with thioflavin-S. Double-labeling experiments demonstrated that all BuChE-positive plaques were Aβ positive, whereas only some BuChE-positive plaques were thioflavin-S positive. These observations suggest that BuChE is associated with a subpopulation of Aβ 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.

Cholinesterase activity associated with neuritic plaques (NPs) and neurofibrillary tangles (NFTs) in Alzheimer's disease (AD) brains exhibit altered histochemical properties, such as requiring lower pH (6.8) for optimal cholinesterase staining compared to the pH (8.0) for best visualization of cholinesterases in neurons. Furthermore, visualization of NPs and NFTs can be prevented by agents like the peptidase inhibitor/metalloantibiotic bacitracin. The anomalous behavior of cholinesterases associated with pathological lesions needs to be elucidated because of the putative links between these enzymes and the disease process in AD. In this study, cholinesterases were extracted from AD and normal brain tissue to determine whether the differences observed in histochemical analyses in the two sources were reflected in kinetic properties measured in solubilized enzymes. Isolated brain enzymes from both these sources exhibited comparable kinetic parameters with respect to pH dependence, substrate affinity and inhibitor sensitivity and were not significantly affected by other agents that blocked cholinesterase histochemical visualization, such as the structurally diverse metal-chelating antibiotics bacitracin, doxycycline, minocycline and rifampicin. Although the cholinesterases from AD brain tissue examined here represented a total pool of these enzymes from AD brain, rather than enzymes specifically from NPs and NFTs, their kinetic behavior being comparable to cholinesterases isolated from normal brain tissues implies that these enzymes do not undergo disease-related modification in their primary structures. This suggests that the atypical histochemical behavior of cholinesterases in NPs and NFTs may result from interaction of cholinesterases with other molecules within these lesions, mediated by transition metal ions known to be present in AD pathology lesions.

The serine hydrolase, butyrylcholinesterase (BChE) is known to have a variety of enzymatic and non-enzymatic functions. In the brain, BChE is expressed mainly in glia, white matter and in distinct populations of neurons in areas important in cognition. In Alzheimer's disease (AD), many β-amyloid (Aβ) plaques become associated with BChE activity, the significance of which is unclear. A mouse model of AD containing five familial AD genes (5XFAD) also exhibits Aβ plaques associated with BChE. We developed a comparable strain (5XFAD/BChE-KO) that is unable to synthesize BChE and reported diminished fibrillar Aβ deposits in the cerebral cortex of 5XFAD/BChE-KO mice, compared to 5XFAD counterparts at the same age. This effect was most significant in male mice. The present study extends comparison of the two strains with a detailed examination of fibrillar Aβ plaque burden in other regions of the brain that typically accumulate pathology and exhibit neurodegeneration. This work demonstrates that, as in the cerebral cortex, the absence of BChE leads to diminished fibrillar Aβ deposition in amygdala, hippocampal formation, thalamus and basal ganglia. This reduction is statistically significant in males, with a trend towards such reduction in female mice.

The cholinergic system plays important roles in neurotransmission in both the peripheral and central nervous systems. The cholinergic neurotransmitter acetylcholine is synthesized by choline acetyltransferase (ChAT) and its action terminated by acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The predominance of AChE has focused much attention on understanding the relationship of this enzyme to ChAT-positive cholinergic neurons. However, there is ample evidence that BuChE also plays an important role in cholinergic regulation. To elucidate the relationship of BuChE to neural elements that are producing acetylcholine, the distribution of this enzyme was compared to that of ChAT in the mouse CNS. Brain tissues from 129S1/SvImJ mice were stained for BuChE and ChAT using histochemical, immunohistochemical and immunofluorescent techniques. Both BuChE and ChAT were found in neural elements throughout the CNS. BuChE staining with histochemistry and immunohistochemistry produced the same distribution of labeling throughout the brain and spinal cord. Immunofluorescent double labeling demonstrated that many nuclei in the medulla oblongata, as well as regions of the spinal cord, had neurons that contained both BuChE and ChAT. BuChE-positive neurons without ChAT were found in close proximity with ChAT-positive neuropil in areas such as the thalamus and amygdala. BuChE-positive neuropil was also found closely associated with ChAT-positive neurons, particularly in tegmental nuclei of the pons. These observations provide further neuroanatomical evidence of a role for BuChE in the regulation of acetylcholine levels in the CNS.

Butyrylcholinesterase (BuChE) is an enzyme capable of hydrolysing a wide variety of esters including acetylcholine, a molecule involved in neurotransmission and modulation of immune cell activity. In the brain, BuChE is expressed in white matter and certain populations of neurons and glia. Multiple sclerosis (MS) is an autoimmune disease affecting white matter characterized by neuroinflammation and neurodegeneration in the central nervous system. Here we demonstrate alterations in BuChE activity in MS white matter lesions, including diminished enzyme activity associated with myelin and an increased activity in cells with microglial morphology. Increased BuChE activity within MS lesions could contribute to the pro-inflammatory immune responses through hydrolysis of acetylcholine and to demyelination through hydrolytic deacylation of myelin proteins such as proteolipid protein. This suggests that BuChE could be a potential target for novel disease-modifying strategies for MS.