Bis(9)-(-)-Meptazinol, a novel dual-binding AChE inhibitor, rescues cognitive deficits and pathological changes in APP/PS1 transgenic mice

A Novel Multifunctional 5,6-Dimethoxy-Indanone-Chalcone-Carbamate Hybrids Alleviates Cognitive Decline in Alzheimer’s Disease by Dual Inhibition of Acetylcholinesterase and Inflammation

Backgrounds

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disease. The treatment of AD through multiple pathological targets may generate therapeutic efficacy better. The multifunctional molecules that simultaneously hit several pathological targets have been of great interest in the intervention of AD.

Methods

Here, we combined the chalcone scaffold with carbamate moiety and 5,6-dimethoxy-indanone moiety to generate a novel multi-target-directed ligand (MTDL) molecule (E)-3-((5,6-dimethoxy-1-oxo-1,3-dihydro-2H-inden-2-ylidene)-methyl)phenylethyl(methyl) carbamate (named AP5). In silico approaches were used to virtually predict the binding interaction of AP5 with AChE, the drug-likeness, and BBB penetrance, and later validated by evaluation of pharmacokinetics (PK) in vivo by LC-MS/MS. Moreover, studies were conducted to examine the potential of AP5 for inhibiting AChE and AChE-induced amyloid-β (Aβ) aggregation, attenuating neuroinflammation, and providing neuroprotection in the APP/PS1 model of AD.

Results

We found that AP5 can simultaneously bind to the peripheral and catalytic sites of AChE by molecular docking. AP5 exhibited desirable pharmacokinetic (PK) characteristics including oral bioavailability (67.2%), >10% brain penetrance, and favorable drug-likeness. AP5 inhibited AChE activity and AChE-induced Aβ aggregation in vivo and in vitro. Further, AP5 lowered Aβ plaque deposition and insoluble Aβ levels in APP/PS1 mice. Moreover, AP5 exerted anti-inflammatory responses by switching microglia to a disease-associated microglia (DAM) phenotype and preventing A1 astrocytes formation. The phagocytic activity of microglial cells to Aβ was recovered upon AP5 treatment. Importantly, chronic AP5 treatment significantly prevented neuronal and synaptic damage and memory deficits in AD mice.

Conclusion

Together, our work demonstrated that AP5 inhibited the AChE activity, decreased Aβ plaque deposition by interfering Aβ aggregation and promoting microglial Aβ phagocytosis, and suppressed inflammation, thereby rescuing neuronal and synaptic damage and relieving cognitive decline. Thus, AP5 can be a new promising candidate for the treatment of AD.

Molecular Insights into Therapeutic Potentials of Hybrid Compounds Targeting Alzheimer's Disease

Alzheimer's disease (AD) is one of the most complex progressive neurological disorders involving degeneration of neuronal connections in brain cells leading to cell death. AD is predominantly detected among elder people (> 65 years), mostly diagnosed with the symptoms of memory loss and cognitive dysfunctions. The multifarious pathogenesis of AD comprises the accumulation of pathogenic proteins, decreased neurotransmission, oxidative stress, and neuroinflammation. The conventional therapeutic approaches are limited to symptomatic benefits and are ineffective against disease progression. In recent years, researchers have shown immense interest in the designing and fabrication of various novel therapeutics comprised of naturally isolated hybrid molecules. Hybrid therapeutic compounds are developed from the combination of pharmacophores isolated from bioactive moieties which specifically target and block various AD-associated pathogenic pathways. The method of designing hybrid molecules has numerous advantages over conventional multitarget drug development methods. In comparison to in silico high throughput screening, hybrid molecules generate quicker results and are also less expensive than fragment-based drug development. Designing hybrid-multitargeted therapeutic compounds is thus a prospective approach in developing an effective treatment for AD. Nevertheless, several issues must be addressed, and additional researches should be conducted to develop hybrid therapeutic compounds for clinical usage while keeping other off-target adverse effects in mind. In this review, we have summarized the recent progress on synthesis of hybrid compounds, their molecular mechanism, and therapeutic potential in AD. Using synoptic tables, figures, and schemes, the review presents therapeutic promise and potential for the development of many disease-modifying hybrids into next-generation medicines for AD.

Pantao Pill Improves the Learning and Memory Abilities of APP/PS1 Mice by Multiple Mechanisms

Background: To explore the effect and mechanisms of Pantao Pill (PTP) on cognitive impairment.

Methods: Network pharmacology was performed to analyze the mechanism of PTP treating cognitive impairment. The targets of PTP and cognitive impairment were predicted and used to construct protein-protein interaction (PPI) networks. The intersection network was selected, and the core network was obtained through topological analysis. Enrichment analysis was conducted to obtain the GOBP terms and KEGG pathways. We then performed experiments to validate the results of the network pharmacology by using an APP/PS1 transgenic mouse model. The APP/PS1 mice were divided into four groups: the model group, the high-dose PTP (3.6 g/kg·d) group, the low-dose PTP (1.8 g/kg·d) group, and the positive control group (donepezil hydrochloride, 2 mg/kg·d). Wild-type (WT) C57 mice served as a normal control group. PTP and donepezil were administered by gavage for 8 weeks.

Results: Network pharmacology showed that PTP might improve cognitive impairment by regulating autophagy, apoptosis, and oxidative stress. For the Morris water maze test, a significant difference was shown in the total swimming distance among groups (p < 0.05) in the positioning navigation experiment, and with training time extension, the swimming speed increased (p < 0.01). In the space probe test, PTP administration significantly reduced the swimming path length and the escape latency of APP/PS1 mice (p < 0.05 or p < 0.01), whereas it had no effect on the swimming speed (p > 0.05). PTP (3.6 g/kg/d) rescued the reduction of norepinephrine and acetylcholine levels (p < 0.05), and increased the acetylcholinesterase concentration (p < 0.05) in the brain tissue. PTP (1.8 g/kg/d) increased the norepinephrine level (p < 0.01). PTP rescued the activity reduction of superoxide dismutase in the brain tissue (p < 0.01) and the neuron cell pyknosis in the hippocampal CA region (p < 0.05). PTP reduced ATG12 and PS1 expression (p < 0.05 or p < 0.01), and increased Bcl-2 expression in the brain tissue (p < 0.05).

Conclusion: PTP can significantly improve the learning and memory abilities of APP/PS1 mice, and the mechanism may be related to the increase of neurotransmitter acetylcholine and norepinephrine levels, the reduction of the excessive autophagic activation, and the suppression of oxidative stress and excessive apoptotic activity.

Downregulation of TREM2 expression exacerbates neuroinflammatory responses through TLR4-mediated MAPK signaling pathway in a transgenic mouse model of Alzheimer's disease

Activation of glial cells and neuroinflammation play an important role in the onset and development of Alzheimer's disease (AD). Triggering receptor expressed on myeloid cells 2 (TREM2) is a microglia-specific receptor in the brain that is involved in regulating neuroinflammation. However, the precise effects of TREM2 on neuroinflammatory responses and its underlying molecular mechanisms in AD have not been studied in detail. Here, we employed a lentiviral-mediated strategy to downregulation of TREM2 expression on microglia in the brain of APPswe/PS1dE9 (APP/PS1) transgenic mice and BV2 cells. Our results showed that downregulation of TREM2 significantly aggravated AD-related neuropathology including Aβ accumulation, peri-plaque microgliosis and astrocytosis, as well as neuronal and synapse-associated proteins loss, which was accompanied by a decline in cognitive ability. The further mechanistic study revealed that downregulation of TREM2 expression initiated neuroinflammatory responses through toll-like receptor 4 (TLR4)-mediated mitogen-activated protein kinase (MAPK) signaling pathway and subsequent stimulating the production of pro-inflammatory cytokines in vivo and in vitro. Moreover, blockade of p38, JNK, and ERK1/2 inhibited the release of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) induced by Aβ_1-42 in TREM2-knocked down BV2 cells. Taken together, these findings indicated that TREM2 might be a potential therapeutic target for AD and other neuroinflammation-related diseases.

microRNA-425 loss mediates amyloid plaque microenvironment heterogeneity and promotes neurodegenerative pathologies

Different cellular and molecular changes underlie the pathogenesis of Alzheimer's disease (AD). Among these, neuron‐specific dysregulation is a necessary event for accumulation of classic pathologies including amyloid plaques. Here, we show that AD‐associated pathophysiology including neuronal cell death, inflammatory signaling, and endolysosomal dysfunction is spatially colocalized to amyloid plaques in regions with abnormal microRNA‐425 (miR‐425) levels and this change leads to focal brain microenvironment heterogeneity, that is, an amyloid plaque‐associated microenvironment (APAM). APAM consists of multiple specific neurodegenerative signature pathologies associated with senile plaques that contribute to the heterogeneity and complexity of AD. Remarkably, miR‐425, a neuronal‐specific regulator decreased in AD brain, maintains a normal spatial transcriptome within brain neurons. We tested the hypothesis that miR‐425 loss correlates with enhanced levels of mRNA targets downstream, supporting APAM and AD progression. A miR‐425‐deficient mouse model has enhanced APP amyloidogenic processing, neuroinflammation, neuron loss, and cognitive impairment. In the APP/PS1 mouse model, intervening with miR‐425 supplementation ameliorated APAM changes and memory deficits. This study reveals a novel mechanism of dysregulation of spatial transcriptomic changes in AD brain, identifying a probable neuronal‐specific microRNA regulator capable of staving off amyloid pathogenesis. Moreover, our findings provide new insights for developing AD treatment strategies with miRNA oligonucleotide(s).

Dimeric Tacrine(10)-hupyridone as a Multitarget-Directed Ligand To Treat Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder with multiple pathological features. Therefore, a multitarget-directed ligands (MTDLs) strategy has been developed to treat AD. We have previously designed and synthesized dimeric tacrine(10)-hupyridone (A10E), a novel tacrine derivative with acetylcholinesterase (AChE) inhibition and brain-derived neurotrophic factor (BDNF) activation activity, by linking tacrine and a fragment of huperzine A. However, it was largely unknown whether A10E could act on other AD targets and produce cognitive-enhancing ability in AD animal models. In this study, A10E could prevent cognitive impairments in APP/PS1 transgenic mice and β-amyloid (Aβ) oligomers-treated mice, with higher potency than tacrine and huperzine A. Moreover, A10E could effectively inhibit Aβ production and deposition, alleviate neuroinflammation, enhance BDNF expression, and elevate cholinergic neurotransmission in vivo. At nanomolar concentrations, A10E could inhibit Aβ oligomers-induced neurotoxicity via the activation of tyrosine kinase receptor B (TrkB)/Akt pathway in SH-SY5Y cells. Furthermore, Aβ oligomerization and fibrillization could be directly disrupted by A10E. Importantly, A10E at high concentrations did not produce obvious hepatotoxicity. Our results indicated that A10E could produce anti-AD neuroprotective effects via the inhibition of Aβ aggregation, the activation of the BDNF/TrkB pathway, the alleviation of neuroinflammation, and the decrease of AChE activity. As MTDLs could produce additional benefits, such as overcoming the deficits of drug combination and enhancing the compliance of AD patients, our results also suggested that A10E might be developed as a promising MTDL lead for the treatment of AD.

Deletion of Dcf1 Reduces Amyloid-β Aggregation and Mitigates Memory Deficits

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease. One of the pathologies of AD is the accumulation of amyloid-β (Aβ) to form senile plaques, leading to a decline in cognitive ability and a lack of learning and memory. However, the cause leading to Aβ aggregation is not well understood. Dendritic cell factor 1 (Dcf1) shows a high expression in the entorhinal cortex neurons and neurofibrillary tangles in AD patients.

OBJECTIVE

Our goal is to investigate the effect of Dcf1 on Aβ aggregation and memory deficits in AD development.

METHODS

The mouse and Drosophila AD model were used to test the expression and aggregation of Aβ, senile plaque formation, and pathological changes in cognitive behavior during dcf1 knockout and expression. We finally explored possible drug target effects through intracerebroventricular delivery of Dcf1 antibodies.

RESULTS

Deletion of Dcf1 resulted in decreased Aβ42 level and deposition, and rescued AMPA Receptor (GluA2) levels in the hippocampus of APP-PS1-AD mice. In Aβ42 AD Drosophila, the expression of Dcf1 in Aβ42 AD flies aggravated the formation and accumulation of senile plaques, significantly reduced its climbing ability and learning-memory. Data analysis from all 20 donors with and without AD patients aged between 80 and 90 indicated a high-level expression of Dcf1 in the temporal neocortex. Dcf1 contributed to Aβ aggregation by UV spectroscopy assay. Intracerebroventricular delivery of Dcf1 antibodies in the hippocampus reduced the area of senile plaques and reversed learning and memory deficits in APP-PS1-AD mice.

CONCLUSION

Dcf1 causes Aβ-plaque accumulation, inhibiting dcf1 expression could potentially offer therapeutic avenues.

TREM2 overexpression rescues cognitive deficits in APP/PS1 transgenic mice by reducing neuroinflammation via the JAK/STAT/SOCS signaling pathway

Overactivated microglia and neuroinflammation are considered to play a crucial role in the progression of Alzheimer's disease (AD). Triggering receptor expressed on myeloid cells-2 (TREM2), a type I transmembrane receptor, expressed uniquely by microglia in the brain, is involved in the neuroinflammatory responses of AD. In this study, to further explore the precise effects of TREM2 on neuroinflammation and the underlying mechanisms in AD, we employed a lentiviral-mediated strategy to overexpress TREM2 in the brain of APPswe/PS1dE9 (APP/PS1) transgenic mice and cultured BV2 cells. Our results showed that TREM2 overexpression rescued cognitive deficits, decreased β-amyloid (Aβ) plaques deposition, reduced synaptic and neuronal loss, as well as ameliorated neuroinflammation. The mechanistic study revealed that these protective effects were likely attributed to inhibition of neuroinflammatory responses through the JAK/STAT/SOCS signaling pathway and subsequent attenuation of pro-inflammatory cytokines. Furthermore, suppression of neuroinflammation might be ascribed to activation of the M2 microglia, as the levels of M2 phenotype markers Arg-1, IL-10 and Ym1 were markedly increased. Similarly, overexpression of TREM2 in BV2 cells also promoted M2 polarization and led to the alleviation of M1 microglial inflammatory responses through JAK/STAT/SOCS signaling pathway, suggesting that TREM2 is an important factor in shifting the microglia from M1 to M2 phenotype. Taken together, our results further provide insights into the role of TREM2 in AD pathogenesis and highlight TREM2 as a potential target against AD.

Silencing of LRP1 Exacerbates Inflammatory Response Via TLR4/NF-κB/MAPKs Signaling Pathways in APP/PS1 Transgenic Mice

Activation of glial cells (including microglia and astrocytes) appears central to the initiation and progression of neuroinflammation in Alzheimer's disease (AD). The low-density lipoprotein receptor-related protein 1 (LRP1) is a major receptor for amyloid-β (Aβ), which plays a critical role in AD pathogenesis. LRP1 regulates inflammatory response by modulating the release of pro-inflammatory cytokines and phagocytosis. However, the effects of LRP1 on microglia- and astrocytic cell-mediated neuroinflammation and their underlying mechanisms in AD remain unclear. Therefore, using APP/PS1 transgenic mice, we found that LRP1 is downregulated during disease progression. Silencing of brain LRP1 markedly exacerbated AD-related neuropathology including Aβ deposition, neuroinflammation, and synaptic and neuronal loss, which was accompanied by a decline in spatial cognitive ability. Further mechanistic study revealed that silencing of LRP1 initiated neuroinflammation by increasing microgliosis and astrogliosis, enhancing pro-inflammatory cytokine production, and regulating toll-like receptor 4 (TLR4)-mediated activation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. Taken together, these findings indicated that LRP1 suppresses microglia and astrocytic cell activation by modulating TLR4/NF-κB/MAPK signaling pathways. Our results further provide insights into the role of LRP1 in AD pathogenesis and highlight LRP1 as a potential therapeutic target for the treatment of AD.

Acetylcholinesterase inhibitors in Alzheimer's disease influence Zinc and Copper homeostasis

BACKGROUND

Alzheimer's disease (AD) is the most common age-related neurodegenerative disease. An altered homeostasis of Zinc (Zn) and Copper (Cu), as well as a dysregulated expression of Zn-regulatory proteins have been previously described in AD. Acetylcholinesterase inhibitors (AChEI) are commonly used as AD treatment to improve cognitive function, but their effect on Zn homeostasis is still unexplored.

OBJECTIVES

The aims of this study were to define the metal dyshomeostasis in AD patients, to investigate AChEI influence on Zn homeostasis and inflammation, and to analyze the relationship between cognitive impairment at two-year follow-up and metal concentrations, considering AChEI use.

METHODS AND RESULTS

84 Healthy Elderly (HE) and 95 AD patients were enrolled (62 AchEI user and 33 AchEI naïve). HE showed similar plasma Zn and Cu concentrations and Cu/Zn ratio in comparison to AChEI users, but significantly higher Zn level, as well as lower Cu amount and Cu/Zn ratio than AChEI naïve patients. Moreover, AChEI users had increased Zn plasma level, reduced Cu amount, Cu/Zn ratio, and IL1β concentration and lower Zip2 lymphocytic expression vs. naïve patients. A multiple linear regression analysis showed that the MMSE score decline after two-year follow-up was reduced by AChEI therapy and was positively associated with plasma Zn decrease over time.

CONCLUSION

Our data revealed that AChEI use may affect peripheral Zn and Cu homeostasis in AD patients, decrease Cu/Zn ratio demonstrating a general reduction of inflammatory status in patients under AChEI treatment. Finally, AChEI influence on circulating Zn could be implicated in the drug-related slowdown of cognitive decline.

A multifunctional bis-(-)-nor-meptazinol-oxalamide hybrid with metal-chelating property ameliorates Cu(II)-induced spatial learning and memory deficits via preventing neuroinflammation and oxido-nitrosative stress in mice

Excess copper exposure is a risk factor of neurodegeneration related to Alzheimer's disease (AD). Evidence indicates that, besides promoting amyloid β aggregation, activation of neuroinflammation and oxido-nitrosative stress (two key pathophysiological processes of AD) may also play important roles in Cu(II)-induced neuronal injury. Therefore, the copper-chelating strategy has gained attention in search for new anti-AD drugs. We previously reported a novel multifunctional compound N¹,N²-bis(3-(S)-meptazinol-propyl) oxalamide (ZLA), a bis-(-)-nor-meptazinol-oxalamide hybrid with properties of dual binding site acetylcholinesterase (AChE) inhibition and Cu(II)/Zn(II) chelation. The present study was aimed to explore its effect on cognitive deficits caused by intrahippocampal injection of Cu(II) in mice. Results showed that ZLA (2, 5 mg/kg; i.p.) treatment significantly ameliorated the Cu(II)-induced impairment of hippocampus-dependent learning and memory, whereas rivastigmine, an AChE inhibitor showing a similar potency of enzyme inhibition to ZLA, had no obvious effect. Immunohistochemical and Western blot analyses revealed that ZLA attenuated the decrease in hippocampal expression of microtubule-associated protein 2 (MAP2, a dendritic marker) in Cu(II)-challenged mice. Further analysis showed that ZLA suppressed the Cu(II)-evoked microglial activation. Moreover, it inhibited the Cu(II)-evoked production of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-1β and expression of inducible nitric oxide synthase in the hippocampus. The Cu(II)-induced oxidative and nitrosative stress in the hippocampus was also attenuated after ZLA treatment. Collectively, these results suggest that ZLA ameliorates the Cu(II)-caused cognitive deficits. Inhibition of neuroinflammation and oxido-nitrosative stress, and thus ameliorating neuronal injury, may be the potential mechanism for the anti-amnesic effect of ZLA.