Old and new acetylcholinesterase inhibitors for Alzheimer's disease

Effects of BIS-MEP on Reversing Amyloid Plaque Deposition and Spatial Learning and Memory Impairments in a Mouse Model of β-Amyloid Peptide- and Ibotenic Acid-Induced Alzheimer's Disease

Alzheimer’s disease (AD) is the main type of dementia and is characterized by progressive memory loss and a notable decrease in cholinergic neuron activity. As classic drugs currently used in the clinic, acetylcholinesterase inhibitors (AChEIs) restore acetylcholine levels and relieve the symptoms of AD, but are insufficient at delaying the onset of AD. Based on the multi-target-directed ligand (MTDL) strategy, bis-(-)-nor-meptazinol (BIS-MEP) was developed as a multi-target AChEI that mainly targets AChE catalysis and the β-amyloid (Aβ) aggregation process. In this study, we bilaterally injected Aβ oligomers and ibotenic acid (IBO) into the hippocampus of ICR mice and then subcutaneously injected mice with BIS-MEP to investigate its therapeutic effects and underlying mechanisms. According to the results from the Morris water maze test, BIS-MEP significantly improved the spatial learning and memory impairments in AD model mice. Compared with the vehicle control, the BIS-MEP treatment obviously inhibited the AChE activity in the mouse brain, consistent with the findings from the behavioral tests. The BIS-MEP treatment also significantly reduced the Aβ plaque area in both the hippocampus and cortex, suggesting that BIS-MEP represents a direct intervention for AD pathology. Additionally, the immunohistochemistry and ELISA results revealed that microglia (ionized calcium-binding adapter molecule 1, IBA1) and astrocyte (Glial fibrillary acidic protein, GFAP) activation and the secretion of relevant inflammatory factors (TNFα and IL-6) induced by Aβ were decreased by the BIS-MEP treatment. Furthermore, BIS-MEP showed more advantages than donepezil (an approved AChEI) as an Aβ intervention. Based on our findings, BIS-MEP improved spatial learning and memory deficits in AD mice by regulating acetylcholinesterase activity, Aβ deposition and the inflammatory response in the brain.

Tacrine(10)-Hupyridone Prevents Post-operative Cognitive Dysfunction via the Activation of BDNF Pathway and the Inhibition of AChE in Aged Mice

Post-operative cognitive dysfunction (POCD) could cause short-term or long-term cognitive disruption lasting weeks or months after anesthesia and surgery in elderly. However, no effective treatment of POCD is currently available. Previous studies indicated that the enhancement of brain-derived neurotrophic factor (BDNF) expression, and the elevation the cholinergic system, might be effective to prevent POCD. In this study, we have discovered that tacrine(10)-hupyridone (A10E), a novel acetylcholinesterase (AChE) inhibitor derived from tacrine and huperzine A, could prevent surgery-induced short-term and long-term impairments of recognition and spatial cognition, as evidenced by the novel object recognition test and Morris water maze (MWM) tests, in aged mice. Moreover, A10E significantly increased the expression of BDNF and activated the downstream Akt and extracellular regulated kinase (ERK) signaling in the surgery-treated mice. Furthermore, A10E substantially enhanced choline acetyltransferase (ChAT)-positive area and decreased AChE activity, in the hippocampus regions of surgery-treated mice, indicating that A10E could prevent surgery-induced dysfunction of cholinergic system, possibly via increasing the synthesis of acetylcholine and the inhibition of AChE. In conclusion, our results suggested that A10E might prevent POCD via the activation of BDNF pathway and the inhibition of AChE, concurrently, in aged mice. These findings also provided a support that A10E might be developed as a potential drug lead for POCD.

Design, synthesis and bioevaluation of tricyclic fused ring system as dual binding site acetylcholinesterase inhibitors

Due to recently discovered non-classical acetylcholinesterase (AChE) function, dual binding-site AChE inhibitors have acquired a paramount attention of drug designing researchers. The unique structural arrangements of AChE peripheral anionic site (PAS) and catalytic site (CAS) joined by a narrow gorge, prompted us to design the inhibitors that can interact with dual binding sites of AChE. Eighteen homo- and heterodimers of desloratadine and carbazole (already available tricyclic building blocks) were synthesized and tested for their inhibition potential against electric eel acetylcholinesterase (eeAChE) and equine serum butyrylcholinesterase (eqBChE). We identified a six-carbon tether heterodimer of desloratadine and indanedione based tricyclic dihydropyrimidine (4c) as potent and selective inhibitor of eeAChE with IC₅₀ value of 0.09 ± 0.003 μM and 1.04 ± 0.08 μM (for eqBChE) with selectivity index of 11.1. Binding pose analysis of potent inhibitors suggest that tricyclic ring is well accommodated into the AChE active site through hydrophobic interactions with Trp84 and Trp279. The indanone ring of most active heterodimer 4b is stabilized into the bottom of the gorge and forms hydrogen bonding interactions with the important catalytic triad residue Ser200.

Detarium microcarpum: A novel source of nutrition and medicine: A review

Detarium microcarpum is a plant indigenous to Africa, which occurs naturally in many African countries, particularly in savannah regions. Its leaves and fruits are used mainly as food and as folk medicine. It has anti-diabetic, antioxidant, and hepatitis C inhibitor properties and has been traditionally utilised in cancer treatment. This review examines published work on the nutritional, pharmacological, and traditional uses of Detarium microcarpum. This plant may become valuable if the fruit, stems, roots, and leaves are extracted for nutraceutical purposes.

Cognitive Decline in Preclinical Alzheimer's Disease: Amyloid-Beta versus Tauopathy

 We perform a large-scale meta-analysis of 51 peer-reviewed 3xTg-AD mouse publications to compare Alzheimer’s disease (AD) quantitative clinical outcome measures, including amyloid-β (Aβ), total tau, and phosphorylated tau (pTau), with cognitive performance in Morris water maze (MWM) and Novel Object Recognition (NOR). “High” levels of Aβ (Aβ₄₀, Aβ₄₂) showed significant but weak trends with cognitive decline (MWM: slope = 0.336, R² = 0.149, n = 259, p < 0.001; NOR: slope = 0.156, R² = 0.064, n = 116, p < 0.05); only soluble Aβ or directly measured Aβ meaningfully contribute. Tau expression in 3xTg-AD mice was within 10–20% of wild type and not associated with cognitive decline. In contrast, increased pTau is directly and significantly correlated with cognitive decline in MWM (slope = 0.408, R² = 0.275, n = 371, p < < 0.01) and NOR (slope = 0.319, R² = 0.176, n = 113, p < 0.05). While a variety of pTau epitopes (AT8, AT270, AT180, PHF-1) were examined, AT8 correlated most strongly with cognition (slope = 0.586, R² = 0.521, n = 185, p < < 0.001). Multiple linear regression confirmed pTau is a stronger predictor of MWM performance than Aβ. Despite pTau’s lower physical concentration than Aβ, pTau levels more directly and quantitatively correlate with 3xTg-AD cognitive decline. pTau’s contribution to neurofibrillary tangles well after Aβ levels plateau makes pTau a viable treatment target even in late-stage clinical AD. Principal component analysis, which included hyperphosphorylation induced by kinases (pGSK3β, GSK3β, CDK5), identified phosphorylated ser9 GSK3β as the primary contributor to MWM variance. In summary, meta-analysis of cognitive decline in preclinical AD finds tauopathy more impactful than Aβ. Nonetheless, complex AD interactions dictate successful therapeutics harness synergy between Aβ and pTau, possibly through the GSK3 pathway.

Association between Age and Changes in Heart Rate Variability after Hemodialysis in Patients with Diabetes

Background: Heart rate variability (HRV) represents changes in the time between successive heart beats, and it has been used to assess the autonomic nervous system. Previous studies have reported autonomic dysfunction in diabetic patients undergoing hemodialysis (HD), however, no studies have evaluated the effects of age on changes in HRV in these patients. The aim of this study was to examine the effects of age on changes in HRV in diabetic HD patients.

Methods: We enrolled 84 diabetic patients receiving maintenance HD. HRV was measured before and after HD to assess changes in HRV (ΔHRV). The patients were divided into two groups based on their age (65 years< or ≥65 years).

Results: Compared to the patients aged <65 years, those aged ≥65 years had a higher high frequency (HF) % (p = 0.032) before HD. The patients aged <65 years had a significant increase in very low frequency, low frequency (LF), and HF after HD. The patients aged ≥65 years had a significant increase in LF, but a significant decrease in HF% after HD. There was a significant interaction between age and change of HF% (p = 0.023) after HD. After multivariate adjustments for clinical, biochemical data and medications, systolic blood pressure, total cholesterol, hemoglobin, and hemoglobin were associated with ΔLF, whereas cerebrovascular disease, systolic blood pressure, and fasting glucose were associated with ΔHF% in patients aged ≥65 years.

Conclusion: Our study demonstrated significant changes in HRV after HD in diabetic patients. In the patients aged ≥65 years, LF was increased, whereas HF% was decreased significantly after HD. Among the HRV parameters, age had an interaction with the change of HF%.

Comprehensive Profiling of Fecal Metabolome of Mice by Integrated Chemical Isotope Labeling-Mass Spectrometry Analysis

Gut microbiota plays important roles in the host health. The host and symbiotic gut microbiota coproduce a large number of metabolites during the metabolism of food and xenobiotics. The analysis of fecal metabolites can provide a noninvasive manner to study the outcome of the host-gut microbiota interaction. Herein, we reported the comprehensive profiling of fecal metabolome of mice by an integrated chemical isotope labeling combined with liquid chromatography-mass spectrometry (CIL-LC-MS) analysis. The metabolites are categorized into several submetabolomes based on the functional moieties (i.e., carboxyl, carbonyl, amine, and thiol) and then analysis of the individual submetabolome was performed. The combined data from the submetabolome form the metabolome with relatively high coverage. To this end, we synthesized stable isotope labeling reagents to label metabolites with different groups, including carboxyl, carbonyl, amine, and thiol groups. We detected 2302 potential metabolites, among which, 1388 could be positively or putatively identified in feces of mice. We then further confirmed 308 metabolites based on our established library of chemically labeled standards and tandem mass spectrometry analysis. With the identified metabolites in feces of mice, we established mice fecal metabolome database, which can be used to readily identify metabolites from feces of mice. Furthermore, we discovered 211 fecal metabolites exhibited significant difference between Alzheimer's disease (AD) model mice and wild type (WT) mice, which suggests the close correlation between the fecal metabolites and AD pathology and provides new potential biomarkers for the diagnosis of AD.

Ethanol Extract of Oldenlandia diffusa Herba Attenuates Scopolamine-Induced Cognitive Impairments in Mice via Activation of BDNF, P-CREB and Inhibition of Acetylcholinesterase

Though Oldenlandia diffusa Herba (ODH) has been known to exhibit anti-cancer and anti-inflammatory effects, its anti-amnestic effect has never been reported so far. The aim of this present study was to elucidate the anti-amnestic effect of ODH. ODH pretreatment significantly reduced escape latency of scopolamine treated Institute of Cancer Research (ICR) mice compared to untreated control groups in a Morris water maze test. Similarly, the passive avoidance test showed that ODH treatment recovered the scopolamine induced amnesia in the ICR mouse model. Concentration of Ach in brains of ODH treated mice was increased compared to that of scopolamine treated mice. In addition, activity of acetylcholinesterase (AChE) was notably decreased by ODH. The protein expression of brain-derived neurotrophic factor (BDNF) and phospho-cAMP response element-binding protein (p-CREB) (Ser133) was increased in ODH pretreated group compared to control group. Consistently, immunohistochemistry (IHC) revealed the elevated expression of brain-derived neurotrophic factor (BDNF) and p-CREB in brains of ODH treated mice compared to the control group. Overall, these findings suggest that ODH has anti-amnestic potential via activation of BDNF and p-CREB and inhibition of AChE in mice with scopolamine induced amnesia.

Synthesis and bioevaluation of new tacrine-cinnamic acid hybrids as cholinesterase inhibitors against Alzheimer's disease

Small molecule cholinesterases inhibitor (ChEI) provides an effective therapeutic strategy to treat Alzheimer's disease (AD). Currently, the discovery of new ChEI with multi-target effect is still of great importance. Herein, we report the synthesis, structure-activity relationship study and biological evaluation of a series of tacrine-cinnamic acid hybrids as new ChEIs. All target compounds are evaluated for their in vitro cholinesterase inhibitory activities. The representatives which show potent activity on cholinesterase, are evaluated for the amyloid β-protein self-aggregation inhibition and in vivo assays. The optimal compound 19, 27, and 30 (human AChE IC₅₀ = 10.2 ± 1.2, 16.5 ± 1.7, and 15.3 ± 1.8 nM, respectively) show good performance in ameliorating the scopolamine-induced cognition impairment and preliminary safety in hepatotoxicity evaluation. These compounds deserve further evaluation for the development of new therapeutic agents against AD.

The current agonists and positive allosteric modulators of α7 nAChR for CNS indications in clinical trials

The alpha-7 nicotinic acetylcholine receptor (α7 nAChR), consisting of homomeric α7 subunits, is a ligand-gated Ca²⁺-permeable ion channel implicated in cognition and neuropsychiatric disorders. Enhancement of α7 nAChR function is considered to be a potential therapeutic strategy aiming at ameliorating cognitive deficits of neuropsychiatric disorders such as Alzheimer's disease (AD) and schizophrenia. Currently, a number of α7 nAChR modulators have been reported and several of them have advanced into clinical trials. In this brief review, we outline recent progress made in understanding the role of the α7 nAChR in multiple neuropsychiatric disorders and the pharmacological effects of α7 nAChR modulators used in clinical trials.

Synthesis, Molecular Modeling, and Evaluation of Novel Sulfonylhydrazones as Acetylcholinesterase Inhibitors for Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia and related to the degeneration of hippocampal cholinergic neurons, which dramatically affects cognitive ability. Acetylcholinesterase (AChE) inhibitors are employed as drugs for AD therapy. Three series of sulfonylhydrazone compounds were designed, and their ability to inhibit AChE was evaluated. Fifteen compounds were synthesized and twelve of them had IC₅₀ values of 0.64-51.09 μM. The preliminary structure-activity relationships indicated that the methylcatechol moiety and arylsulfonyl substituents generated better compounds than both the benzodioxole and alkylsulfonyl chains. Molecular dynamics studies of compound 6d showed that the interaction with the peripheral binding site of AChE was similar to donepezil, which may explain its low IC₅₀ (0.64 μM). Furthermore, the drug-likeness of 6d suggests that the compound may have appropriate oral absorption and brain penetration. Compound 6d also presented antiradical activity and was not cytotoxic to LL24 cells, suggesting that this compound might be considered safe. Our findings indicate that arylsulfonylhydrazones may be a promising scaffold for the design of new drug candidates for the treatment of AD.

Synthesis and pharmacological evaluation of multi-functional homoisoflavonoid derivatives as potent inhibitors of monoamine oxidase B and cholinesterase for the treatment of Alzheimer's disease

A series of homoisoflavonoid derivatives was designed, synthesized and evaluated as potential multi-functional anti-Alzheimer's agents for their inhibitory activity on cholinesterase and monoamine oxidase. Among them, compound 16 showed moderate acetylcholinesterase (AChE) inhibitory activity (eeAChE IC50 = 0.89 ± 0.02 μM; hAChE IC50 = 0.657 ± 0.002 μM) and significant monoamine oxidase B (MAO-B) inhibitory activity (hMAO-B IC50 = 0.0372 ± 0.0002 μM). Kinetic analysis of AChE, MAO-B inhibition and molecular modeling studies revealed that compound 16 is a dual binding site inhibitor of AChE and noncompetitive inhibitor of MAO-B. Furthermore, 16 could penetrate through the blood-brain barrier (BBB) in vitro. Most importantly, oral administration of 16 demonstrated no marked signs of acute toxicity and it could significantly reverse scopolamine-induced memory impairment in mice. These results suggested that compound 16 is a promising multifunctional drug candidate with potential effect for the treatment of Alzheimer's disease.

Targeting Free Radicals in Oxidative Stress-Related Human Diseases

Cancer and Alzheimer's disease (AD) are characterized by (i) opposing biological mechanisms, (ii) an inverse correlation between their incidences, and (iii) oxidative stress being a common denominator of both diseases. Increased formation of reactive oxygen species (ROS) in cancer cells from oncogenic signaling and/or metabolic disturbances leads to upregulation of cellular antioxidant capacity to maintain ROS levels below a toxic threshold. Combining drugs that induce high levels of ROS with compounds that suppress cellular antioxidant capacity by depleting antioxidant systems [glutathione (GSH), superoxide dismutase (SOD), and thioredoxin (TRX)] and/or targeting glucose metabolism represents a potential anticancer strategy. In AD, free metals and/or Aβ:metal complexes may cause damage to biomolecules in the brain (via Fenton reaction), including DNA. Metal chelation, based on the application of selective metal chelators or metal delivery, may induce neuroprotective signaling and represents a promising therapeutic strategy. This review examines therapeutic strategies based on the modulation of oxidative stress in cancer and AD.

Discovery of potential inhibitor against human acetylcholinesterase: a molecular docking and molecular dynamics investigation

Alzheimer's disease (AD) is a progressive neurodegenerative disease of central nervous system among elderly people. Human acetylcholinesterase (hAChE), an important enzyme in neuronal signaling, is responsible for the degradation of acetylcholine which in turn prevents the post synaptic signal transmissions. hAChE has been an attractive target of drug discovery for the search of therapeutics against AD. In the recent past hAChE has become hot target for the investigation of new potential therapeutics. We performed virtual screening of entire database against hAChE. Further, the extra precision molecular docking was carried out to refine the docking results and the best complex was passed for molecular dynamics simulations in order of understanding the hAChE dynamics and its behavior in complex with the ligand which corroborate the outcomes of virtual screening. This also provides binding free energy data that establishes the ligands efficiency for inhibiting hAChE. The computational findings discussed in this paper provide initial information of inhibitory effects of ligand, (drugbank entry DB00983), over hAChE.