Cysteine thioesters as myelin proteolipid protein analogues to examine the role of butyrylcholinesterase in myelin decompaction

New insights into butyrylcholinesterase: Pharmaceutical applications, selective inhibitors and multitarget-directed ligands

Butyrylcholinesterase (BChE), also known as pseudocholinesterase and serum cholinesterase, is an isoenzyme of acetylcholinesterase (AChE). It mediates the degradation of acetylcholine, especially under pathological conditions. Proverbial pharmacological applications of BChE, its mutants and modulators consist of combating Alzheimer's disease (AD), influencing multiple sclerosis (MS), addressing cocaine addiction, detoxifying organophosphorus poisoning and reflecting the progression or prognosis of some diseases. Of interest, recent reports have shed light on the relationship between BChE and lipid metabolism. It has also been proved that BChE is going to increase abnormally as a compensator for AChE in the middle and late stages of AD, and BChE inhibitors can alleviate cognitive disorders and positively influence some pathological features in AD model animals, foreboding favorable prospects and potential applications. Herein, the selective BChE inhibitors and BChE-related multitarget-directed ligands published in the last three years were briefly summarized, along with the currently known pharmacological applications of BChE, aiming to grasp the latest research directions. Thereinto, some emerging strategies for designing BChE inhibitors are intriguing, and the modulators based on target combination of histone deacetylase and BChE against AD is unprecedented. Furthermore, the involvement of BChE in the hydrolysis of ghrelin, the inhibition of low-density lipoprotein (LDL) uptake, and the down-regulation of LDL receptor (LDLR) expression suggests its potential to influence lipid metabolism disorders. This compelling prospect likely stimulates further exploration in this promising research direction.

Possible Role of Butyrylcholinesterase in Fat Loss and Decreases in Inflammatory Levels in Patients with Multiple Sclerosis after Treatment with Epigallocatechin Gallate and Coconut Oil: A Pilot Study

(1) Background. Multiple sclerosis (MS) is characterised by the loss of muscle throughout the course of the disease, which in many cases is accompanied by obesity and related to inflammation. Nonetheless, consuming epigallocatechin gallate (EGCG) and ketone bodies (especially β-hydroxybutyrate (βHB)) produced after metabolising coconut oil, have exhibited anti-inflammatory effects and a decrease in body fat. In addition, butyrylcholinesterase (BuChE), seems to be related to the pathogenesis of the disease associated with inflammation, and serum concentrations have been related to lipid metabolism. Objective. The aim of the study was to determine the role of BuChE in the changes caused after treatment with EGCG and ketone bodies on the levels of body fat and inflammation state in MS patients. (2) Methods. A pilot study was conducted for 4 months with 51 MS patients who were randomly divided into an intervention group and a control group. The intervention group received 800 mg of EGCG and 60 mL of coconut oil, and the control group was prescribed a placebo. Fat percentage and concentrations of the butyrylcholinesterase enzyme (BuChE), paraoxonase 1 (PON1) activity, triglycerides, interleukin 6 (IL-6), albumin and βHB in serum were measured. (3) Results. The intervention group exhibited significant decreases in IL-6 and fat percentage and significant increases in BuChE, βHB, PON1, albumin and functional capacity (determined by the Expanded Disability Status Scale (EDSS)). On the other hand, the control group only exhibited a decrease in IL-6. After the intervention, BuChE was positively correlated with the activity of PON1, fat percentage and triglycerides in the intervention group, whereas these correlations were not observed in the control group (4). Conclusions. BuChE seems to have an important role in lipolytic activity and the inflammation state in MS patients, evidenced after administering EGCG and coconut oil as a βHB source.

The Effects of Repetitive Transcranial Magnetic Stimulation on Cognitive Impairment and the Brain Lipidome in a Cuprizone-Induced Mouse Model of Demyelination

The protective effects of repetitive transcranial magnetic stimulation (rTMS) on myelin integrity have been extensively studied, and growing evidence suggests that rTMS is beneficial in improving cognitive functions and promoting myelin repair. However, the association between cognitive improvement due to rTMS and changes in brain lipids remains elusive. In this study, we used the Y-maze and 3-chamber tests, as well as a mass spectrometry-based lipidomic approach in a CPZ-induced demyelination model in mice to assess the protective effects of rTMS on cuprizone (CPZ)-induced cognitive impairment and evaluate changes in lipid composition in the hippocampus, prefrontal cortex, and striatum. We found that CPZ induced cognitive impairment and remarkable changes in brain lipids, specifically in glycerophospholipids. Moreover, the changes in lipids within the prefrontal cortex were more extensive, compared to those observed in the hippocampus and striatum. Notably, rTMS ameliorated CPZ-induced cognitive impairment and partially normalized CPZ-induced lipid changes. Taken together, our data suggest that rTMS may reverse cognitive behavioral changes caused by CPZ-induced demyelination by modulating the brain lipidome, providing new insights into the therapeutic mechanism of rTMS.

Shenzhiling oral solution promotes myelin repair through PI3K/Akt-mTOR pathway in STZ-induced SAD mice

Most forms of Alzheimer's disease are sporadic. A model of sporadic Alzheimer's disease induced with bilateral intraventricular injection of streptozotocin leads to insulin resistance in the brain accompanied by memory decline, synaptic dysfunction, amyloid plaque deposition, oxidative stress, and neuronal apoptosis, all of which mimic the pathologies associated with sporadic Alzheimer's disease. Myelin injury is an essential component of Alzheimer's disease, playing a key role in early cognitive impairment. Our previously research found that sporadic Alzheimer's disease model showed myelin injury and that Shenzheling oral solution improved mild-to-moderate Alzheimer's disease; therefore, the protective effect of Shenzheling oral solution on myelin injury in early cognitive impairment is worth attention. In this study, the Morris water maze test results showed impairments in the learning and memory functions of mice in the model group, whereas the learning and memory function significantly improved after drug intervention. Immunohistochemistry showed increased β-amyloid plaques in the model group and decreased amounts in the drug group. Moreover, results of electron microscopy, western blot, and polymerase chain reaction showed that Shenzhiling oral solution improved early cognitive impairment and repaired myelin sheath damage; the potential mechanism of these effects may relate to the PI3K/Akt-mTOR signaling pathway. These findings support the application and promotion of Shenzhiling oral solution to treat sporadic Alzheimer's disease.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02900-x.

Structure and therapeutic uses of butyrylcholinesterase: Application in detoxification, Alzheimer's disease, and fat metabolism

Structural information of butyrylcholinesterase (BChE) and its variants associated with several diseases are discussed here. Pure human BChE has been proved safe and effective in treating organophosphorus (OPs) poisoning and has completed Phase 1 and 2 pharmacokinetic (PK) and safety studies. The introduction of specific mutations into native BChE to endow it a self-reactivating property has gained much progress in producing effective OPs hydrolases. The hydrolysis ability of native BChE on cocaine has been confirmed but was blocked to clinical application due to poor PK properties. Several BChE mutants with elevated cocaine hydrolysis activity were published, some of which have shown safety and efficiency in treating cocaine addiction of human. The increased level of BChE in progressed Alzheimer's disease patients made it a promising target to elevate acetylcholine level and attenuate cognitive status. A variety of selective BChE inhibitors with high inhibitory activity published in recent years are reviewed here. BChE could influence the weight and insulin secretion and resistance of BChE knockout (KO) mice through hydrolyzing ghrelin. The BChE-ghrelin pathway could also regulate aggressive behaviors of BChE-KO mice.

Imaging Butyrylcholinesterase in Multiple Sclerosis

PURPOSE

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.

PROCEDURE

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.

RESULTS

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.

CONCLUSIONS

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.

Central and peripheral anti-inflammatory effects of acetylcholinesterase inhibitors

Acetylcholinesterase (AChE) inhibitors modulate acetylcholine hydrolysis and hence play a key role in determining the cholinergic tone and in implementing its impact on the cholinergic blockade of inflammatory processes. Such inhibitors may include rapidly acting small molecule AChE-blocking drugs and poisonous anti-AChE insecticides or war agent inhibitors which penetrate both body and brain. Notably, traumatized patients may be hyper-sensitized to anti-AChEs due to their impaired cholinergic tone, higher levels of circulation pro-inflammatory cytokines and exacerbated peripheral inflammatory responses. Those largely depend on the innate-immune system yet reach the brain via vagus pathways and/or disrupted blood-brain-barrier. Other regulators of the neuro-inflammatory cascade are AChE-targeted microRNAs (miRs) and synthetic chemically protected oligonucleotide blockers thereof, whose size prevents direct brain penetrance. Nevertheless, these larger molecules may exert parallel albeit slower inflammatory regulating effects on brain and body tissues. Additionally, oligonucleotide aptamers interacting with innate immune Toll-Like Receptors (TLRs) may control inflammation through diverse routes and in different rates. Such aptamers may compete with the action of both small molecule inhibitors and AChE-inhibiting miRs in peripheral tissues including muscle and intestine. However, rapid adaptation processes, visualized in neuromuscular junctions enable murine survival under otherwise lethal anti-cholinesterase exposure; and both miR inhibitors and TLR-modulating aptamers may exert body-brain signals protecting experimental mice from acute inflammation. The complex variety of AChE inhibiting molecules identifies diverse body-brain communication pathways which may rapidly induce long-lasting central reactions to peripheral stressful and inflammatory insults in both mice and men. This article is part of the special issue entitled 'Acetylcholinesterase Inhibitors: From Bench to Bedside to Battlefield'.

Cholinergic signaling in myelination

There is a long history of research on acetylcholine (ACh) function in myelinating glia, but a resurgence of interest recently as a result of the therapeutic potential of manipulating ACh signaling to promote remyelination, and the broader interest in neurotransmitter signaling in activity-dependent myelination. Myelinating glia express all the major types of muscarinic and nicotinic ACh receptors at different stages of development, and acetylcholinesterase and butyrylcholinesterase are highly expressed in white matter. This review traces the history of research on ACh signaling in Schwann cells, oligodendrocytes, and in the myelin sheath, and summarizes current knowledge on the intracellular signaling and functional consequences of ACh signaling in myelinating glia. Implications of ACh in diseases, such as Alzheimer's disease, multiple sclerosis, and white matter toxicity caused by pesticides are considered, together with an outline of major questions for future research. GLIA 2017;65:687-698.