Scopolamine, a Toxin-Induced Experimental Model, Used for Research in Alzheimer’s Disease

Oligosaccharides from black ginseng innovatively prepared by low-temperature steam-heating process ameliorate cognitive impairment in Alzheimer's disease mice via the Keap-1/Nrf2 pathway

BACKGROUND

Our objective in this study was to evaluate the effectiveness of oligosaccharides extracted from black ginseng (OSBG), innovatively prepared by a low-temperature steam-heating process, in the improvement of learning and memory impairment in mice, as well as the mechanism(s).

RESULTS

Eight carbohydrates involving isomaltose and maltotetraose were detected in black gensing; monosaccharide residues including mannose and rhamnose were also discovered. OSBG-treated mice showed significant amelioration in recognition and spatial memory deficits compared to the scopolamine group. OSBG could decrease acetylcholinesterase activity in a tissue-dependent fashion but not in a dose-dependent manner. Furthermore, in contrast, OSBG administration resulted in significant upregulation superoxide dismutase, glutathione, glutathione peroxidase (GPx), and Kelch-like ECH-associated protein 1, downregulation of malondialdehyde and nuclear factor erythroid 2-related factor 2 in the tissues. Finally, at the genus level, we observed that the OSBG interventions increased the relative abundance of probiotics (e.g., Barnesiella, Staphylococcus, Clostridium_XlVb) and decreased pernicious bacteria such as Eisenbergiella and Intestinimonas, compared to the Alzheimer's disease mouse model group. Herein, our results demonstrate that OSBG restores the composition of the scopolamine-induced intestinal microbiota in mice, providing homeostasis of gut microbiota and providing evidence for microbiota-regulated therapeutic potential.

CONCLUSION

Our results showed for the first time a clear role for OSBG in improving scopolamine-induced memory impairment by inhibiting cholinergic dysfunction in a tissue-dependent manner. Additionally, OSBG administration relieved oxidative stress by activating the Keap-1/Nrf2 pathway and modulating the gut microbiota. Collectively, OSBG may be a promising target for neuroprotective antioxidants for improving memory and cognition in Alzheimer's disease patients. © 2024 Society of Chemical Industry.

Tailored Melatonin- and Donepezil-Based Hybrids Targeting Pathognomonic Changes in Alzheimer's Disease: An In Vitro and In Vivo Investigation

A plethora of pathophysiological events have been shown to play a synergistic role in neurodegeneration, revealing multiple potential targets for the pharmacological modulation of Alzheimer's disease (AD). In continuation to our previous work on new indole- and/or donepezil-based hybrids as neuroprotective agents, the present study reports on the beneficial effects of lead compounds of the series on key pathognomonic features of AD in both cellular and in vivo models. An enzyme-linked immunosorbent assay (ELISA) was used to evaluate the anti-fibrillogenic properties of 15 selected derivatives and identify quantitative changes in the formation of neurotoxic β-amyloid (Aβ42) species in human neuronal cells in response to treatment. Among the most promising compounds were 3a and 3c, which have recently shown excellent antioxidant and anticholinesterase activities, and, therefore, have been subjected to further in vivo investigation in mice. An acute toxicity study was performed after intraperitoneal (i.p.) administration of both compounds, and 1/10 of the LD50 (35 mg/kg) was selected for subacute treatment (14 days) with scopolamine in mice. Donepezil (DNPZ) and/or galantamine (GAL) were used as reference drugs, aiming to establish any pharmacological superiority of the multifaceted approach in battling hallmark features of neurodegeneration. Our promising results give first insights into emerging disease-modifying strategies to combine multiple synergistic activities in a single molecule.

In Vitro and In Vivo Investigations of Chromone Derivatives as Potential Multitarget-Directed Ligands: Cognitive Amelioration Utilizing a Scopolamine-Induced Zebrafish Model

Alzheimer's disease is a complex neurological disorder linked with multiple pathological hallmarks. The interrelation of therapeutic targets assists in the enhancement of cognitive decline through interference with overall neuronal transmission. We have synthesized and screened various chromone derivatives as potential multitarget-directed ligands for the effective treatment of Alzheimer's disease. The synthesized compounds exhibited multipotent activity against AChE, BuChE, MAO-B, and amyloid β aggregation. Three potent compounds, i.e., VN-3, VN-14, and VN-19 were identified that displayed remarkable activities against different targets. These compounds displayed IC50 values of 80 nM, 2.52 μM, and 140 nM against the AChE enzyme, respectively, and IC50 values of 2.07 μM, 70 nM, and 450 nM against the MAO-B isoform, respectively. VN-3 displayed potent activity against self-induced Aβ1-42 aggregation with inhibition of 58.3%. In the ROS inhibition studies, the most potent compounds reduced the intracellular ROS levels up to 80% in SH-SY5Y cells at 25 μM concentration. The compounds were found to be neuroprotective and noncytotoxic even at a concentration of 25 μM against SH-SY5Y cells. In silico studies showed that the compounds were nicely accommodated in the active sites of the receptors along with thermodynamically stable orientations. Compound VN-19 exhibited a balanced multitargeting profile against AChE, BuChE, MAO-B, and Aβ1-42 enzymes and was further evaluated for in vivo activities on the scopolamine-induced zebrafish model. VN-19 was found to ameliorate the cognitive decline in zebrafish brains by protecting them against scopolamine-induced neurodegeneration. Thus, VN-3, VN-14, and VN-19 were identified as potent multitarget-directed ligands with a balanced activity profile against different targets and can be developed as therapeutics for AD.

Nelumbo nucifera leaves extract ameliorated scopolamine-induced cognition impairment via enhanced adult hippocampus neurogenesis

In this presentation, we explored the molecular mechanisms of N. nucifera leaf water extracts (NLWEs) and polyphenol extract (NLPE) on scopolamine-induced cell apoptosis and cognition defects. The administration of NLWE and NLPE did not alter the body weight and serum biomarker rs and significantly ameliorated scopolamine-induced cognition impairment according to Y-maze test analysis. In mice, treatment with scopolamine disrupted normal histoarchitecture in the hippocampus, whereas the administration of NLWE and NLPE reversed the phenomenon. Western blot analysis revealed that scopolamine mitigated the expression of doublecortin (DCX), nestin, and NeuN, and cotreatment with NLWE or NLPE significantly recovered the expression of these proteins. NLWE and NLPE upregulated DCX and NeuN expression in the hippocampus region, as evidenced by immunohistochemical staining analysis of scopolamine-treated mice. NLWE and NLPE obviously elevated brain-derived neurotrophic factor (BDNF) and enhanced its downstream proteins activity. NLWE and NLPE attenuated scopolamine-induced apoptosis by reducing Bax and increased Bcl-2 expression. In addition, scopolamine also triggered apoptosis in human neuroblastoma SH-SY5Y cells whereas co-treatment with NLWE or quercetin-3-glucuronide (Q3G) reversed the phenomenon. NLWE or Q3G enhanced Bcl-2 and reduced Bax expression in the presence of scopolamine in SH-SY5Y cells. NLWE or Q3G recovered the inhibitory effects of scopolamine on neurogenesis and BDNF signals in SH-SY5Y cells. Overall, our results revealed that N. nucifera leaf extracts and Q3G promoted adult hippocampus neurogenesis and prevented apoptosis to mitigate scopolamine-induced cognition dysfunction through the regulation of BDNF signaling pathway.

The Effect of a Tribulus-Based Formulation in Alleviating Cholinergic System Impairment and Scopolamine-Induced Memory Loss in Zebrafish (Danio rerio): Insights from Molecular Docking and In Vitro/In Vivo Approaches

Tribulus terrestris L. (Tt) has been recently gaining attention for its pharmacological value, including its neuroprotective activities. In this study, we explore the neuroprotective effects of a Tribulus terrestris extract in a zebrafish (Danio rerio) model of scopolamine (SCOP)-induced memory impairment and brain oxidative stress. SCOP, an anticholinergic drug, was employed to replicate fundamental aspects of Alzheimer's disease (AD) in animal models. The fish were treated with ethanolic leaf extract (ELE) from Tt (1, 3, and 6 mg/L) for 15 days. SCOP (100 µM) was administered 30 min before behavioral tests were conducted. Molecular interactions of the major compounds identified via UPLC-PDA/MS in Tt fractions with the active site of acetylcholinesterase (AChE) were explored via molecular docking analyses. Terrestrosin C, protodioscin, rutin, and saponin C exhibited the most stable binding. The spatial memory performance was assessed using the Y-maze test, and memory recognition was examined using a novel object recognition (NOR) test. Tt extract treatment reversed the altered locomotion patterns that were caused by SCOP administration. Biochemical analyses also verified Tt's role in inhibiting AChE, improving antioxidant enzyme activities, and reducing oxidative stress markers. The present findings pave the way for future application of Tt as a natural alternative to treat cognitive disorders.

New insights in animal models of neurotoxicity-induced neurodegeneration

The high prevalence of neurodegenerative diseases is an unintended consequence of the high longevity of the population, together with the lack of effective preventive and therapeutic options. There is great pressure on preclinical research, and both old and new models of neurodegenerative diseases are required to increase the pipeline of new drugs for clinical testing. We review here the main models of neurotoxicity-based animal models leading to central neurodegeneration. Our main focus was on studying how changes in neurotransmission and neuroinflammation, mainly in rodent models, contribute to harmful processes linked to neurodegeneration. The majority of the models currently in use mimic Parkinson's disease (PD) and Alzheimer's disease (AD), which are the most common neurodegenerative conditions in older adults. AD is the most common age-related dementia, whereas PD is the most common movement disorder with also cases of dementia. Several natural toxins and xenobiotic agents induce dopaminergic neurodegeneration and can reproduce neuropathological traits of PD. The literature analysis of MPTP, 6-OH-dopamine, and rotenone models suggested the latter as a useful model when specific doses of rotenone were administrated systemically to C57BL/6 mice. Cholinergic neurodegeneration is mainly modelled with the toxin scopolamine, which is a useful rodent model for the screening of protective drugs against cognitive decline and AD. Several agents have been used to model neuroinflammation-based neurodegeneration and dementia in AD, including lipopolysaccharide (LPS), streptozotocin, and monomeric C-reactive protein. The bacterial agent LPS makes a useful rodent model for testing anti-inflammatory therapies to halt the development and severity of AD. However, neurotoxin models might be more useful than genetic models for drug discovery in PD but that is not the case in AD where they cannot beat the new developments in transgenic mouse models. Overall, we should work using all available models, either in vivo, in vitro, or in silico, considering the seriousness of the moment and urgency of developing effective drugs.

Insight into the emerging and common experimental in-vivo models of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial, rapidly progressing neurodegenerative disorder. As the exact cause of the disease is still unclear, the drug development is very challenging. This review encompasses the commonly used AD models involving various chemicals, heavy metals and endogenous substances induced models and the transgenic models. It also provides insight into the reliable emerging models of AD that may overcome the shortcomings associated with available models. Chemicals like streptozotocin, scopolamine, colchicine and okadaic acid render the animal susceptible to neuroinflammation and oxidative stress induced neurodegeneration along with amyloid-β deposition and tau hyperphosphorylation. Similarly, endogenous substances like acrolein and amyloid-β 1-42 are efficient in inducing the major pathologies of AD. Heavy metals like aluminum and fluoride and mixture of these have been reported to induce neurotoxicity therefore are used as animal models for AD. Transgenic models developed as a result of knock-in or knock-out of certain genes associated with AD including PDAPP, APP23, Tg2576, APP/PS1, 3 × Tg and 5 × FAD have also been incorporated in this study. Further, emerging and advanced pathomimetic models of AD are provided particular interest here which will add on to the current knowledge of animal models and may aid in the drug development process and deepen our understanding related to AD pathogenesis. These newly discovered models include oAβ25-35 model, transgenic model expressing 82-kDa ChAT, oDGal mouse and APP knock-in rat. This study may aid in the selection of suitable model for development of novel potent therapeutics and for exploring detailed pathogenic mechanism of AD.

The Effects and Mechanisms of Xanthones in Alzheimer's Disease: A Systematic Review

Xanthones are natural secondary metabolites that possess great potential as neuroprotective agents due to their prominent biological effects on Alzheimer's disease (AD). However, their underlying mechanisms in AD remain unclear. This study aimed to systematically review the effects and mechanisms of xanthones in cell culture and animal studies, gaining a better understanding of their roles in AD. A comprehensive literature search was conducted in the Medline and Scopus databases using specific keywords to identify relevant articles published up to June 2023. After removing duplicates, all articles were imported into the Rayyan software. The article titles were screened based on predefined inclusion and exclusion criteria. Relevant full-text articles were assessed for biases using the OHAT tool. The results were presented in tables. Xanthones have shown various pharmacological effects towards AD from the 21 preclinical studies included. Cell culture studies demonstrated the anti-cholinesterase activity of xanthones, which protects against the loss of acetylcholine. Xanthones exhibited neuroprotective effects by promoting cell viability, reducing the accumulation of β-amyloid and tau aggregation. The administration of xanthones in animal models resulted in a reduction in neuronal inflammation by decreasing microglial and astrocyte burden. In terms of molecular mechanisms, xanthones prevented neuroinflammation through the modulation of signaling pathways, including TLR4/TAK1/NF-κB and MAPK pathways. Mechanisms such as activation of caspase-3 and -9 and suppression of endoplasmic reticulum stress were also reported. Despite the various neuroprotective effects associated with xanthones, there are limited studies reported on their underlying mechanisms in AD. Further studies are warranted to fully understand their potential roles in AD.

Preclinical Studies of Canagliflozin, a Sodium-Glucose Co-Transporter 2 Inhibitor, and Donepezil Combined Therapy in Alzheimer's Disease

The incidence of neurodegenerative diseases, such as Alzheimer's disease (AD), is continuously growing worldwide, which leads to a heavy economic and societal burden. The lack of a safe and effective causal therapy in cognitive decline is an aggravating factor and requires investigations into the repurposing of commonly used drugs. Sodium-glucose co-transporter 2 inhibitors (SGLT2i) are a new and efficient class of hypoglycemic drugs and, due to their pleiotropic effects, have indications that go beyond diabetes. There is emerging data from murine studies that SGLT2i can cross the blood-brain barrier and may have neuroprotective effects, such as increasing the brain-derived neurotrophic factor (BDNF), reducing the amyloid burden, inhibiting acetylcholinesterase (AChE) and restoring the circadian rhythm in the mammalian target of rapamycin (mTOR) activation. The current study investigates the effect of an SGLT2i and donepezil, under a separate or combined 21-day treatment on AD-relevant behaviors and brain pathology in mice. The SGLT2i canagliflozin was found to significantly improve the novelty preference index and the percentage of time spent in the open arms of the maze in the novel object recognition and elevated plus maze test, respectively. In addition, canagliflozin therapy decreased AChE activity, mTOR and glial fibrillary acidic protein expression. The results also recorded the acetylcholine M1 receptor in canagliflozin-treated mice compared to the scopolamine group. In the hippocampus, the SGLT2i canagliflozin reduced the microgliosis and astrogliosis in males, but not in female mice. These findings emphasize the value of SGLT2i in clinical practice. By inhibiting AChE activity, canagliflozin represents a compound that resembles AD-registered therapies in this respect, supporting the need for further evaluation in dementia clinical trials.

Neuroprotective Effects of Davallia mariesii Roots and Its Active Constituents on Scopolamine-Induced Memory Impairment in In Vivo and In Vitro Studies

Beta-amyloid (Aβ) proteins, major contributors to Alzheimer's disease (AD), are overproduced and accumulate as oligomers and fibrils. These protein accumulations lead to significant changes in neuronal structure and function, ultimately resulting in the neuronal cell death observed in AD. Consequently, substances that can inhibit Aβ production and/or accumulation are of great interest for AD prevention and treatment. In the course of an ongoing search for natural products, the roots of Davallia mariesii T. Moore ex Baker were selected as a promising candidate with anti-amyloidogenic effects. The ethanol extract of D. mariesii roots, along with its active constituents, not only markedly reduced Aβ production by decreasing β-secretase expression in APP-CHO cells (Chinese hamster ovary cells which stably express amyloid precursor proteins), but also exhibited the ability to diminish Aβ aggregation while enhancing the disaggregation of Aβ aggregates, as determined through the Thioflavin T (Th T) assay. Furthermore, in an in vivo study, the extract of D. mariesii roots showed potential (a tendency) for mitigating scopolamine-induced memory impairment, as evidenced by results from the Morris water maze test and the passive avoidance test, which correlated with reduced Aβ deposition. Additionally, the levels of acetylcholine were significantly elevated, and acetylcholinesterase levels significantly decreased in the brains of mice (whole brains). The treatment with the extract of D. mariesii roots also led to upregulated brain-derived neurotrophic factor (BDNF) and phospho-cAMP response element-binding protein (p-CREB) in the hippocampal region. These findings suggest that the extract of D. mariesii roots, along with its active constituents, may offer neuroprotective effects against AD. Consequently, there is potential for the development of the extract of D. mariesii roots and its active constituents as effective therapeutic or preventative agents for AD.

Levistilide A ameliorates neuroinflammation via inhibiting JAK2/STAT3 signaling for neuroprotection and cognitive improvement in scopolamine-induced Alzheimer's disease mouse model

Alzheimer's disease (AD) is a progressive neurodegenerative disease associated with cognitive impairment and dementia, which has become a major public health problem. There are no effective therapeutic agents used to treat AD in clinic for the extremely complex pathogenesis. Here we identify Levistilide A (LA), one of the major active natural terpene lactone constituents from Chinese herbal medicine Angelicae sinensis and Chuanxiong Rhizoma, as a potent neuroinflammation inhibitor for neuroprotection and cognitive improvement of AD. We show that LA suppresses neuronal apoptosis, restores cholinergic system function, and lowers neuroinflammation in vivo to improve scopolamine (SCOP)-induced learning and memory deficits. In addition, LA inhibits the release of IL-1β, IL-6 and TNF-α, while increasing the production of IL-4 and IL-10 for anti-inflammatory effects in LPS or Aβ-induced BV2 and HMC3 cells. Furthermore, the conditioned medium (CM) from LA-treated BV2 or HMC3 cells enhances the viability of SH-SY5Y and HT-22 cells, and LA reverses M1 to M2 phenotype transformation of BV2 and HMC3 cells accompanied by the inhibited Iba-1 expression and mRNA level of IL-1β, IL-6, TNF-α and NOS2, and the increased expression of ARG1, CD206 and CD163. Mechanistically, we analyze JAK2/STAT3 signaling as possible targets of LA using network pharmacology approaches, and further experimentally validate that LA inhibits the phosphorylation of JAK2 and STAT3, and STAT3 expression within nucleus both in vitro and in vivo. Collectively, we identify LA as a potential neuroinflammation inhibitor for neuroprotection and cognitive improvement, which is expected to be a candidate for AD therapy.

Oral Administration of Egg- and Soy-Derived Lysophosphatidylcholine Mitigated Acetylcholine Depletion in the Brain of Scopolamine-Treated Rats

Enzyme-modified lecithin that contains lysophosphatidylcholine (LPC) is generally recognized as safe. However, its potential as a functional ingredient has been less investigated than other choline (Ch)-containing compounds, such as glycerophosphocholine (GPC). Reports on the possibility of LPC functioning as a cholinergic precursor in vivo and on its kinetics are limited to docosahexaenoic acid-bound LPC. Herein, three experiments were performed to investigate these processes in scopolamine (SCO)-treated rats. First, an egg-derived LPC reagent was orally administered to rats, and brain acetylcholine (ACh), Ch, plasma Ch, and LPC were measured. Second, soy- and rapeseed-derived enzyme-modified lecithins and GPC were administered for comparison. Third, soy-derived enzyme-modified lecithins with different fat contents were administered for comparison. The LPC reagent mitigated SCO-induced ACh depletion at 500 mg/kg body weight and increased plasma Ch, but not LPC, concentrations. Additionally, soy-derived LPC-containing food additive counteracted brain ACh depletion similarly to GPC. Interestingly, plasma Ch and linoleoyl-LPC levels were higher when soy-derived LPC with a higher fat content was administered, whereas the plasma levels of palmitoyl-LPC decreased and those of total LPC remained constant. In conclusion, egg- and soy-derived LPC species function as cholinergic precursors in vivo, and future studies should explore this potential.

The Proof-of-Concept of MBA121, a Tacrine-Ferulic Acid Hybrid, for Alzheimer's Disease Therapy

Great effort has been devoted to the synthesis of novel multi-target directed tacrine derivatives in the search of new treatments for Alzheimer's disease (AD). Herein we describe the proof of concept of MBA121, a compound designed as a tacrine-ferulic acid hybrid, and its potential use in the therapy of AD. MBA121 shows good β-amyloid (Aβ) anti-aggregation properties, selective inhibition of human butyrylcholinesterase, good neuroprotection against toxic insults, such as Aβ1-40, Aβ1-42, and H2O2, and promising ADMET properties that support translational developments. A passive avoidance task in mice with experimentally induced amnesia was carried out, MBA121 being able to significantly decrease scopolamine-induced learning deficits. In addition, MBA121 reduced the Aβ plaque burden in the cerebral cortex and hippocampus in APPswe/PS1ΔE9 transgenic male mice. Our in vivo results relate its bioavailability with the therapeutic response, demonstrating that MBA121 is a promising agent to treat the cognitive decline and neurodegeneration underlying AD.

Polygoni Multiflori Radix Praeparata and Acori Tatarinowii Rhizoma ameliorate scopolamine-induced cognitive impairment by regulating the cholinergic and synaptic associated proteins

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Polygoni Multiflori Radix Praeparata (PMRP) and Acori Tatarinowii Rhizoma (ATR) is often used in traditional Chinese medicine to prevent and treat Alzheimer's disease (AD). However, it is not clear whether the effects and mechanisms of the decoction prepared by traditional decocting method (PA) is different from that prepared by modern decocting method (P + A).

AIM OF THE STUDY

The present study aimed to investigate the differences in the protective effects of PA and P + A on scopolamine induced cognitive impairment, and to explore its potential mechanism.

MATERIALS AND METHODS

To assess the protective effect of PA and P + A on cognitive dysfunction, the mice were orally administrated with PA (1.56, 6.24 g kg^-1•day^-1) and P + A (1.56, 6.24 g kg^-1•day^-1) for 26 days before co-treatment with scopolamine (4 mg kg^-1•day^-1, i.p.). The learning and memory abilities of mice were examined by Morris water maze test, and the expressions of proteins related to cholinergic system and synaptic function were detected by the methods of ELISA, real-time PCR and Western blotting. Then, molecular docking technique was used to verify the effect of active compounds in plasma after PA administration on Acetylcholinesterase (AChE) protein. Finally, the Ellman method was used to evaluate the effects of different concentrations of PA, P + A (1 μg/mL-100 mg/mL) and the compounds (1-100 μM) on AChE activity in vitro.

RESULTS

On one hand, in the scopolamine-induced cognitive impairment mouse model, both of PA and P + A could improve the cognitive impairment, while the effect of PA on cognitive amelioration was better than that of P + A. Moreover, PA regulated the cholinergic and synaptic functions by enhancing the concentration of acetylcholine (ACh), the mRNA levels of CHT1, Syn, GAP-43 and PSD-95, and the related proteins (CHT1, VACHT, Syn, GAP-43 and PSD-95), and significantly inhibiting the expression of AChE protein. Meanwhile, P + A only up-regulated the mRNA levels of GAP-43 and PSD-95, increased the expressions of CHT1, VACHT, Syn, GAP-43 and PSD-95 proteins, and inhibited the expression of AChE protein. On the other hand, the in vitro study showed that some compounds including emodin-8-o-β-d-Glucopyranoside, THSG and α-Asarone inhibited AChE protein activity with the IC₅₀ values 3.65 μM, 5.42 μM and 9.43 μM, respectively.

CONCLUSIONS

These findings demonstrate that both of PA and P + A can ameliorate the cognitive deficits by enhancing cholinergic and synaptic related proteins, while PA has the stronger improvement effect on the cholinergic function, which may be attributed to the compounds including THSG, emodin, emodin-8-O-β-D-glucopyranoside and α-asarone. The present study indicated that PA has more therapeutic potential in the treatment of neurodegenerative diseases such as AD. The results provide the experimental basis for the clinical use of PA.

Spontaneous and familial models of Alzheimer's disease: Challenges and advances in preclinical research

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder that is progressive and irreversible in nature. Even after decades of dedicated research and paradigm-shifting hypotheses of AD etiology, very few well-founded credible improvements have been foreseen in understanding the actual underlying mechanisms involved in the development of the disorder. As for any disease to be well-comprehended, AD also requires optimal modelling strategies, which will then pave way for effective therapeutic interventions. Most of the clinical trials and research towards better treatment of AD fail in translation, due to the inefficacy of explored animal models to mimic the actual AD pathology, precisely. The majority of the existing AD models are developed based on the mutations found in the familial form of AD (fAD) which accounts for less than 5 % of the incidence of AD. Further, the investigations also face more challenges due to the additional complexities and lacunae found in etiology of sporadic form of AD (sAD), which accounts for 95 % of total AD. This review illustrates the gaps found in different models of AD, both sporadic and familial variants with additional focus on recent avenues for accurate simulation of AD pathology using in vitro and chimeric AD models.

Spotlight on Coenzyme Q10 in scopolamine-induced Alzheimer's disease: oxidative stress/PI3K/AKT/GSK 3ß/CREB/BDNF/TrKB

OBJECTIVES

Excess amyloid beta (Aβ) and oxidative stress (OS) are inextricable hallmarks of the neuronal damage associated Alzheimer's disease. Aβ-induced cognitive and memory dysfunctions are mediated through different signalling pathways as phosphatidylinositol-3-kinase (PI3K) and their downstream intermediates including protein-kinase-B, known as Akt, glycogen-synthase-kinase-3β (GSK-3β), cAMP-response-element-binding-protein (CREB), brain-derived-neurotrophic factor (BDNF) and tropomyosin-related-kinase receptor-B (TrKB). The current work aims to investigate the protective potentials of CoQ10 against scopolamine (Scop)-induced cognitive disability and the contribution of PI3K/Akt/GSK-3β/CREB/BDNF/TrKB in the neuroprotection effects.

METHODS

The chronic co-administration of CQ10 (50, 100 and 200 mg/kg/day i.p.) with Scop in Wistar rats for 6 weeks were assayed both behaviourally and biochemically.

KEY FINDINGS

CoQ10 ameliorated the Scop-induced cognitive and memory defects by restoring alterations in novel object recognition and Morris water maze behavioural tests. CoQ10 favourably changed the Scop-induced deleterious effects in hippocampal malondialdehyde, 8-hydroxy-2' deoxyguanosine, antioxidants and PI3K/Akt/GSK-3β/CREB/BDNF/TrKB levels.

CONCLUSIONS

These results exhibited the neuroprotective effects of CoQ10 on Scop-induced AD and revealed its ability to inhibit oxidative stress, amyloid deposition and to modulate PI3K/Akt/GSK-3β/CREB/BDNF/TrKB pathway.

A Comparative Study of the Impact of NO-Related Agents on MK-801- or Scopolamine-Induced Cognitive Impairments in the Morris Water Maze

Learning and memory deficits accompany numerous brain dysfunctions, including schizophrenia and Alzheimer’s disease (AD), and many studies point to the role of nitric oxide (NO) in these processes. The present investigations constitute the follow-up of our previous research, in which we investigated the activity of NO releasers and a selective inhibitor of neuronal NO synthase (nNOS) to prevent short-term memory deficits in novel object recognition and T-maze. Here, the ability of the compounds to prevent the induction of long-term memory deficits by MK-801 or scopolamine administration was investigated. The Morris Water Maze test, a reliable and valid test of spatial learning and memory, was used, in which escape latency in the acquisition phase and nine different parameters in the retention phase were measured. A fast NO releaser (spermine NONOate), a slow NO releaser (DETA NONOate), and a nNOS inhibitor, N(ω)-propyl-L-arginine (NPLA), were used. The compounds were administered i.p. at a dose range of 0.05–0.5 mg/kg. All compounds prevented learning deficits in the acquisition phase and reversed reference memory deficits in the retention phase of the scopolamine-treated mice. Spermine NONOate was the least effective. In contrast, the drugs poorly antagonised MK-801-induced deficits, and only the administration of DETA NONOate induced some improvements in the retention trial.

Promnesic, Anxiolytic and Antioxidant Effects of Glaucosciadium cordifolium (Boiss.) Burtt & Davis Essential Oil in a Zebrafish Model of Cognitive Impairment

The purpose of this study was to investigate the effect of Glaucosciadium cordifolium essential oil (GCEO, 25 and 150 µL/L) on anxiety and learning and memory impairment induced by scopolamine (SCOP) in zebrafish. The chemical composition was analyzed by GC-MS, and the results showed that the highest content was limonene followed by α- and β-pinene, p-cymene and α-phellandrene. The dementia model was induced by SCOP (100 µM), whereas GCEO and galantamine (GAL, 1 mg/L) were delivered to the SCOP-induced model. It was found that GCEO significantly improved memory impairment and anxiety-like response induced by SCOP through the Y-maze, novel object recognition (NOR) test, and novel tank diving tests (NTT). Biochemical analyses showed that GCEO reduced SCOP-induced oxidative damage. Additionally, the cholinergic system activity was improved in the SCOP-induced model by decreasing the acetylcholinesterase (AChE) activity following the exposure to GCEO. It was clear that as a mixture, GCEO displays positive action in improving memory impairment through restoring cholinergic dysfunction and brain antioxidant status.

A Multifunctional (-)-Meptazinol-Serotonin Hybrid Ameliorates Oxidative Stress-Associated Apoptotic Neuronal Death and Memory Deficits via Activating the Nrf2/Antioxidant Enzyme Pathway

The pathogenesis of Alzheimer's disease (AD) involves multiple pathophysiological processes. Oxidative stress is a major cause of AD-associated neuronal injury. The current research was designed to examine whether a novel (-)-meptazinol-serotonin hybrid (Mep-S) with potent antioxidant activity and additional inhibitory properties for acetylcholinesterase (AChE) activity could attenuate oxidative neuronal damage and cognitive deficits. In human SH-SY5Y cells, Mep-S suppressed H₂O₂-induced apoptosis by restoring mitochondrial membrane potential and inhibiting caspase-3 activation. Meanwhile, it attenuated oxidative stress elicited by H₂O₂ through lessening generation of reactive oxygen species as well as enhancing production of glutathione (GSH) and activity of superoxide dismutase (SOD). Mechanistically, Mep-S promoted nuclear translocation of a transcription factor nuclear factor E2-related factor-2 (Nrf2) in H₂O₂-challenged cells. This effect was accompanied by reduction in Kelch-like ECH-associated protein-1 (Keap1) levels as well as augmentation of Akt phosphorylation and expression of heme oxygenase-1 (HO-1) and NAD(P)H quinine oxidoreductase-1 (NQO-1). Molecular docking analysis revealed that Mep-S may disrupt the protein-protein interactions between Keap1 and Nrf2. In an in vivo mouse model, Mep-S attenuated scopolamine-caused cognitive deficits with inhibition of apoptotic neuronal death and brain AChE activity. Furthermore, the scopolamine-induced impairment of total antioxidant capacity and reduction in SOD1, SOD2, and γ-glutamate-cysteine ligase expression in the brain were counteracted by Mep-S, accompanied by decreased Keap1 levels, increased Akt catalytic subunit and Nrf2 phosphorylation, and decreased Nrf2, HO-1, and NQO-1 expression. Collectively, our results suggest that Mep-S ameliorates apoptotic neuronal death and memory dysfunction associated with oxidative stress by regulating the Nrf2/antioxidant enzyme pathway through inactivating Keap1 and phosphorylating Nrf2 via Akt activation. Therefore, Mep-S may be a potential lead for multitarget neuroprotective agents to treat AD-like symptoms.

Smart Farming Enhances Bioactive Compounds Content of Panax ginseng on Moderating Scopolamine-Induced Memory Deficits and Neuroinflammation

Korean ginseng (Panax ginseng) is a traditional herbal supplement known to have a variety of pharmacological activities. A smart farm system could provide potential standardization of ginseng seedlings after investigating plant metabolic responses to various parameters in order to design optimal conditions. This research was performed to investigate the effect of smart-farmed ginseng on memory improvement in a scopolamine-induced memory deficit mouse model and an LPS-induced microglial cell model. A smart farming system was applied to culture ginseng. The administration of its extract (S2 extract) under specific culture conditions significantly attenuated cognitive and spatial memory deficits by regulating AKT/ERK/CREB signaling, as well as the cortical inflammation associated with suppression of COX-2 and NLRP3 induced by scopolamine. In addition, S2 extract improved the activation of iNOS and COX-2, and the secretion of NO in LPS-induced BV-2 microglia. Based on the HPLC fingerprint and in vitro data, ginsenosides Rb2 and Rd were found to be the main contributors to the anti-inflammatory effects of the S2 extract. Our findings suggest that integrating a smart farm system may enhance the metabolic productivity of ginseng and provides evidence of its potential impact on natural bioactive compounds of medicinal plants with beneficial qualities, such as ginsenosides Rb2 and Rd.

Pathogenesis, Animal Models, and Drug Discovery of Alzheimer's Disease

Alzheimer's disease (AD), the most common cause of dementia, is a chronic neurodegenerative disease induced by multiple factors. The high incidence and the aging of the global population make it a growing global health concern with huge implications for individuals and society. The clinical manifestations are progressive cognitive dysfunction and lack of behavioral ability, which not only seriously affect the health and quality of life of the elderly, but also bring a heavy burden to the family and society. Unfortunately, almost all the drugs targeting the classical pathogenesis have not achieved satisfactory clinical effects in the past two decades. Therefore, the present review provides more novel ideas on the complex pathophysiological mechanisms of AD, including classical pathogenesis and a variety of possible pathogenesis that have been proposed in recent years. It will be helpful to find out the key target and the effect pathway of potential drugs and mechanisms for the prevention and treatment of AD. In addition, the common animal models in AD research are outlined and we examine their prospect for the future. Finally, Phase I, II, III, and IV randomized clinical trials or on the market of drugs for AD treatment were searched in online databases (Drug Bank Online 5.0, the U.S. National Library of Medicine, and Alzforum). Therefore, this review may also provide useful information in the research and development of new AD-based drugs.

Preclinical Models for Alzheimer's Disease: Past, Present, and Future Approaches

A robust preclinical disease model is a primary requirement to understand the underlying mechanisms, signaling pathways, and drug screening for human diseases. Although various preclinical models are available for several diseases, clinical models for Alzheimer's disease (AD) remain underdeveloped and inaccurate. The pathophysiology of AD mainly includes the presence of amyloid plaques and neurofibrillary tangles (NFT). Furthermore, neuroinflammation and free radical generation also contribute to AD. Currently, there is a wide gap in scientific approaches to preventing AD progression. Most of the available drugs are limited to symptomatic relief and improve deteriorating cognitive functions. To mimic the pathogenesis of human AD, animal models like 3XTg-AD and 5XFAD are the primarily used mice models in AD therapeutics. Animal models for AD include intracerebroventricular-streptozotocin (ICV-STZ), amyloid beta-induced, colchicine-induced, etc., focusing on parameters such as cognitive decline and dementia. Unfortunately, the translational rate of the potential drug candidates in clinical trials is poor due to limitations in imitating human AD pathology in animal models. Therefore, the available preclinical models possess a gap in AD modeling. This paper presents an outline that critically assesses the applicability and limitations of the current approaches in disease modeling for AD. Also, we attempted to provide key suggestions for the best-fit model to evaluate potential therapies, which might improve therapy translation from preclinical studies to patients with AD.

PPARγ activation improved learning and memory and attenuated oxidative stress in the hippocampus and cortex of aged rats

Oxidative stress has an important role in brain aging and its consequences include cognitive decline and physiological disorders. Peroxisome proliferator-activated receptor-γ (PPARγ) activation has been suggested to decrease oxidative stress. In the current research, the effect of PPARγ activation by pioglitazone(Pio) on learning, memory and oxidative stress was evaluated in aged rats. The rats were divided into five groups. In the Control group, vehicle (saline-diluted dimethyl sulfoxide (DMSO)) and saline were injected instead of Pio and scopolamine (Sco), respectively. In the Sco group, the vehicle was injected instead of Pio and the rats were injected by Sco 30 min before the behavioral tests. In the Sco-Pio 10, Sco-Pio 20, and Sco-Pio 30 groups, 10, 20, and 30 mg/kg Pio was injected and finally, the rats were injected with Sco 30 min before the behavioral tests. Morris water mater maze(MWM) and passive avoidance(PA) tests were carried out, and finally, the hippocampus and cortex were removed for biochemical assessments. The results showed that the highest dose of Pio decreased the traveling time and distance during 5 days of learning and increased the time and distance in the target area on the probe day of MWM. The highest dose of Pio also prolonged the delay time for entering the dark and total time spent in the light while decreasing the total time spent in and the number of entries into the dark in PA test. Pio especially, in the medium and highest doses, decreased MDA while increasing thiol, superoxide dismutase, and catalase in the hippocampus and cortex. It is concluded that PPARγ activation by Pio as an agonist improved learning and memory in aged rats probably by attenuating oxidative stress in the hippocampus and cortex.

Yuk-Gunja-Tang attenuates neuronal death and memory impairment via ERK/CREB/BDNF signaling in the hippocampi of experimental Alzheimer’s disease model

Yuk-Gunja-Tang (YG) is the Korean traditional medicine in East Asia for gastrointestinal disorders. In the present study, we determined the protective effects of YG on glutamate-induced cytotoxicity in HT22 hippocampal neuronal cells and mice with scopolamine-induced memory impairment. In vitro assessments were performed using a cell viability assay, flow cytometry, and Western blotting, while in vivo assessments were performed in C57BL/6 mice administered with YG for 7 days and injected with scopolamine (1 mg/kg) for 7 days. We assessed the memory function using the Y-maze, novel object recognition, and passive avoidance tests. Protein expression analyses and histological analyses were performed using hippocampal tissues. YG treatment significantly restored cell viability against glutamate-induced apoptosis. It significantly suppressed glutamate-induced reactive oxygen species accumulation and mitochondrial dysfunction. It also increased Bcl-2 protein expression and decreased HO-1 protein expression. It activated the extracellular signal-regulated kinase/cAMP response element binding protein (ERK/CREB) signaling pathway and increased the expression of brain-derived neurotrophic factor (BDNF) under excitotoxic conditions. In the scopolamine-injected mice, YG ameliorated memory impairment in the Y-maze, novel object recognition, and passive avoidance tests; restored dysfunction in the acetylcholine, acetylcholinesterase expression levels; reduced neuronal damage in Nissl staining; and increased BDNF and phosphorylated ERK and CREB levels in Western blotting and immunofluorescence staining. Thus, YG exerted neuroprotective effects by activating ERK/CREB/BDNF signaling in the hippocampus, indicating its potential cognition-enhancing effects, especially in Alzheimer’s disease.

Minocycline attenuates cholinergic dysfunction and neuro-inflammation-mediated cognitive impairment in scopolamine-induced Alzheimer's rat model

OBJECTIVE

Minocycline, a semisynthetic tetracycline-derived antibiotic, has various pharmacological effect such as anti-inflammatory, anti-oxidative stress, and anti-apoptotic effects. The current study investigated the involvement of neuro-inflammatory, oxidative stress, and cholinergic markers in neuroprotection by minocycline against scopolamine-induced brain damage.

METHODS

Minocycline was administered (oral, 10, 15, and 30 mg/kg, daily) to groups of amnesic rats for 21 days. Passive avoidance memory and spatial learning and memory were assessed. Following that, oxidative stress, cholinergic function, and neuro-inflammation markers were evaluated in the brain tissue.

RESULTS

According to our biochemical data, treatment of the scopolamine-injured rats with minocycline decreased the levels of malondialdehyde and acetylcholinesterase (AChE) as well as mRNA expression of AChE and neuro-inflammation markers (tumor necrosis factor-α, interleukin (IL)-1β, IL-6). It also increased the total thiol levels and superoxide dismutase activity as well as mRNA expression of cholinergic receptor M1 (ChRM1). Moreover, minocycline modified distance and latencies in Morris water maze, prolonged latency to enter the black zone and light time while decreasing time spent and frequency of entries to darkness.

CONCLUSION

Taken together, the data indicate that treatment with minocycline improved memory dysfunction mediated possibly through restoring AChE and ChRM1 levels, oxidant/antioxidant balance, as well as inhibiting inflammatory responses.

Trimethoxyflavones from Ocimum basilicum L. leaves improve long term memory in mice by modulating multiple pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Traditionally, Ocimum basilicum L. leaves (OB) are recommended for various brain disorders.

AIM OF THE STUDY

Scientific evidence highlights the cognition improvement capacity of Ocimum basilicum L. leave extract (OBE), however, the compound(s) responsible for this effect and the associated mechanism was not reported. The present study was, thus, designed to isolate and identify the compound responsible for memory improvement effects of OB and to delineate the associated mechanism of action.

MATERIALS AND METHODS

In-vitro acetylcholinesterase (AChE) inhibitory (Ellman method) and antioxidant (DPPH scavenging) assays guided fractionation was employed to isolate the bioactive compounds from OBE. The isolated compounds were characterised using spectroscopic techniques (FTIR, NMR and MS). In-silico and in-vivo [mouse model of scopolamine (SCOP) induced amnesia] investigations were used to substantiate the memory improvement effects of isolated compounds and to understand their mechanism of action.

RESULTS

AChE and DPPH assays guided fractionation of OBE lead to isolation of two pure compounds namely, 5,7-dihydroxy-3',4',5'-trimethoxyflavone (S1) and 3-hydroxy-3',4',5'-trimethoxyflavone (S2). Both S1 and S2 mitigated the cognitive impairment due to SCOP in mice by reducing brain AChE activity, TBARS, TNF-α, IL-1β, IL-6 and caspase-3 concentrations and elevating reduced glutathione and IL-10 levels; together with amelioration of brain hippocampus histopathological aberration (H and E staining). Moreover, the molecular docking of S1 and S2 at the active pockets of AChE and caspase-3 has shown good interactions with vital amino acid residues.

CONCLUSIONS

Our findings show that trimethoxy flavones are responsible for the memory improvement effect of OBE due to their anticholinergic, antioxidant, anti-inflammatory and anti-apoptotic properties. These maybe developed as valuable alternatives for management of cognitive disorders.

Friedelin Attenuates Neuronal Dysfunction and Memory Impairment by Inhibition of the Activated JNK/NF-κB Signalling Pathway in Scopolamine-Induced Mice Model of Neurodegeneration

Oxidative stress (OS) and c-Jun N-terminal kinase (JNK) are both key indicators implicated in neuro-inflammatory signalling pathways and their respective neurodegenerative diseases. Drugs targeting these factors can be considered as suitable candidates for treatment of neuronal dysfunction and memory impairment. The present study encompasses beneficial effects of a naturally occurring triterpenoid, friedelin, against scopolamine-induced oxidative stress and neurodegenerative pathologies in mice models. The treated animals were subjected to behavioural tests i.e., Y-maze and Morris water maze (MWM) for memory dysfunction. The underlying mechanism was determined via western blotting, antioxidant enzymes and lipid profile analyses. Molecular docking studies were carried out to predict the binding modes of friedelin in the binding pocket of p-JNK protein. The results reveal that scopolamine caused oxidative stress by (1) inhibiting catalase (CAT), peroxidase enzyme (POD), superoxide dismutase (SOD), and reduced glutathione enzyme (GSH); (2) the up-regulation of thiobarbituric acid reactive substances (TBARS) in mice brain; and (3) affecting the neuronal synapse (both pre- and post-synapse) followed by associated memory dysfunction. In contrast, friedelin administration not only abolished scopolamine-induced oxidative stress, glial cell activation, and neuro-inflammation but also inhibited p-JNK and NF-κB and their downstream signaling molecules. Moreover, friedelin administration improved neuronal synapse and reversed scopolamine-induced memory impairment accompanied by the inhibition of β-secretase enzyme (BACE-1) to halt amyloidogenic pathways of amyloid-β production. In summary, all of the results show that friedelin is a potent naturally isolated neuro-therapeutic agent to reverse scopolamine-induced neuropathology, which is characteristic of Alzheimer’s disease.

Potential Roles of α-amylase in Alzheimer's Disease: Biomarker and Drug Target

Alzheimer's disease (AD), the most common form of dementia, is pathologically characterized by the deposition of amyloid-β plaques and the formation of neurofibrillary tangles. In a neurodegenerative brain, glucose metabolism is also impaired and considered as one of the key features in AD patients. The impairment causes a reduction in glucose transporters and the uptake of glucose as well as alterations in the specific activity of glycolytic enzymes. Recently, it has been reported that α-amylase, a polysaccharide-degrading enzyme, is present in the human brain. The enzyme is known to be associated with various diseases such as type 2 diabetes mellitus and hyperamylasaemia. With this information at hand, we hypothesize that α-amylase could have a vital role in the demented brains of AD patients. This review aims to shed insight into the possible link between the expression levels of α-amylase and AD. Lastly, we also cover the diverse role of amylase inhibitors and how they could serve as a therapeutic agent to manage or stop AD progression.

The Brilliance of the Zebrafish Model: Perception on Behavior and Alzheimer’s Disease

Alzheimer’s disease (AD) has become increasingly prevalent in the elderly population across the world. It’s pathophysiological markers such as overproduction along with the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFT) are posing a serious challenge to novel drug development processes. A model which simulates the human neurodegenerative mechanism will be beneficial for rapid screening of potential drug candidates. Due to the comparable neurological network with humans, zebrafish has emerged as a promising AD model. This model has been thoroughly validated through research in aspects of neuronal pathways analogous to the human brain. The cholinergic, glutamatergic, and GABAergic pathways, which play a role in the manifested behavior of the zebrafish, are well defined. There are several behavioral models in both adult zebrafish and larvae to establish various aspects of cognitive impairment including spatial memory, associative memory, anxiety, and other such features that are manifested in AD. The zebrafish model eliminates the shortcomings of previously recognized mammalian models, in terms of expense, extensive assessment durations, and the complexity of imaging the brain to test the efficacy of therapeutic interventions. This review highlights the various models that analyze the changes in the normal behavioral patterns of the zebrafish when exposed to AD inducing agents. The mechanistic pathway adopted by drugs and novel therapeutic strategies can be explored via these behavioral models and their efficacy to slow the progression of AD can be evaluated.

Cholinergic models of memory impairment in animals and man: scopolamine vs. biperiden

Scopolamine has been used as a pharmacologic model for cognitive impairments in dementia and Alzheimer's disease. The validity of this model seems to be limited because findings in animals do not readily translate to novel treatments in humans. Biperiden is also a cholinergic deficit model for cognitive impairments but specifically blocks muscarinic M1 receptors. The effects of scopolamine and biperiden (and pirenzepine) are compared in animal studies and related to findings in humans. It is concluded that the effects on cognitive functions are different for scopolamine and biperiden, and they should be considered as different cognitive deficit models. Scopolamine may model more advanced stages of Alzheimer's disease whereas biperiden may model the early deficits in declarative memory in aging and mild cognitive impairment.

Samhwangsasim-tang attenuates neuronal apoptosis and cognitive decline through BDNF-mediated activation of tyrosin kinase B and p75-neurotrophin receptors

BACKGROUND

Samhwangsasim-tang (SST) is a traditional medicine used to treat hypertension and arteriosclerosis. Additionally, due to the effects of its constituent herbs, SST is considered effective for memory-related disorders.

PURPOSE

We investigated the effects of SST on neuronal survival and memory in glutamate-induced hippocampal cells and in a mouse model of scopolamine-induced memory impairment.

METHODS

SST components were identified using 3D-ultra performance liquid chromatography (3D-UPLC). In vitro, we induced glutamate-induced excitotoxicity in HT22 cells after SST pretreatment. We used a cell counting kit-8 and cell cytotoxicity assay, flow cytometry, and western blotting to test the protective effects of SST on neuronal death. In vivo, C57BL/6J mice were administered with 150 and 300 mg/kg SST once daily for 7 days and then intraperitoneally injected with 1 mg/kg scopolamine for 7 days to induce cognitive impairment. We then measured cognitive behavior using a novel object recognition test (NORT) and passive avoidance test (PAT) and analyzed the histological and protein changes.

RESULTS

Our results showed that treatment with 50 and 100 μg/ml SST provided significant protection against glutamate-induced cell death. Flow cytometry and western blotting results suggested that 100 μg/ml SST treatment reduced oxidative stress and mitochondrial dysfunction. SST treatment also increased brain-derived neurotrophic factor (BDNF), its receptor, TrkB receptor, and cAMP-response element binding protein (CREB) activation while reducing the P75NTR and JNK signaling activation. Our in vivo results showed that SST administration improved cognitive impairment, similar to donepezil treatment (as a positive control), in NORT and PAT. SST and donepezil decreased neuronal cell death and apoptosis, and acetylcholine levels were increased in the scopolamine-treated hippocampus. Additionally, SST promoted CREB phosphorylation and BDNF maturation while reducing JNK and P75NTR activation; in contrast, donepezil did not alter levels of these proteins in the scopolamine-treated mouse hippocampus.

CONCLUSION

Our results suggest that SST has neuroprotective effects to attenuate neuronal cell death and oxidative stress through CREB/JNK signaling via BDNF activation. SST may regulate endogenous survival factors in the hippocampus, which may be a safe and potential clinical treatment for cognitive impairment in AD.

Protective Effect of Ginsenosides from Stems and Leaves of Panax ginseng against Scopolamine-Induced Memory Damage via Multiple Molecular Mechanisms

Although growing evidence has shown that ginsenosides from stems and leaves of Panax ginseng (GSLS) exercise a protective impact on the central nervous system, in the model of memory damage induced by scopolamine, it is still rarely reported. Thus, the mechanism of action needs to be further explored. This study was to investigate the effect of GSLS on scopolamine (SCOP)-induced memory damage and the underlying mechanism. Male ICR mice were treated with SCOP (3 mg/kg) for 7 days, with or without GSLS (75 and 150 mg/kg) treatment for 14 days. After GSLS treatment, the memory damage induced by SCOP was significantly ameliorated as shown by the improvement of cholinergic function (AChE and ChAT), brain tissue hippocampus morphology (H&E staining), and oxidative stress (MDA, GSH, and NO). Meanwhile, immunohistochemical assay suggested that GSLS increased the expression of brain-derived neurotrophic factor (BDNF) and Tyrosine Kinase receptor B (TrkB). Further mechanism research indicated that GSLS inhibited the Tau hyperphosphorylation and cell apoptosis by regulating the PI3K/AKT pathway and inhibited neuroinflammation by regulating the NF-κB pathway, thereby exerting a cognitive impairment improvement effect. This work suggested that GSLS could protect against SCOP-induced memory defects possibly through inhibiting oxidative stress, inhibiting neuroinflammation and cell apoptosis.

Chinese Herbal Extracts Exert Neuroprotective Effect in Alzheimer’s Disease Mouse Through the Dopaminergic Synapse/Apoptosis Signaling Pathway

Background: Alzheimer’s disease (AD) as an age-related, irreversible neurodegenerative disease, characterized by cognitive dysfunction, has become progressively serious with a global rise in life expectancy. As the failure of drug elaboration, considerable research effort has been devoted to developing therapeutic strategies for treating AD. TCM is gaining attention as a potential treatment for AD. Gastrodia elata Blume, Polygala tenuifolia Willd., Cistanche deserticola Ma, Rehmannia lutinosa (Gaertn.)DC., Acorus gramineus Aiton, and Curcuma longa L. (GPCRAC) are all well-known Chinese herbs with neuroprotective benefits and are widely used in traditional Chinese decoction for AD therapy. However, the efficacy and further mechanisms of GPCRAC extracts in AD experimental models are still unclear. The purpose of this study was to investigate the synergistic protective efficacy of GPCRAC extracts (composed of extracts from these six Chinese medicines), and the protein targets mediated by GPCRAC extracts in treating AD.

Methods: Scopolamine-induced cognitive impairment mouse model was established to determine the neuroprotective effects of GPCRAC extracts in vivo, as shown by behavioral tests and cerebral cholinergic function assays. To identify the potential molecular mechanism of GPCRAC extracts against AD, label-free quantitative proteomics coupled with tandem mass spectrometry (LC-MS/MS) were performed. The integrated bioinformatics analysis was applied to screen the core differentially expressed proteins in vital canonical pathways. Critical altered proteins were validated by qPCR and Western blotting.

Results: Administration of GPCRAC extracts significantly recovered scopolamine-induced cognitive impairment, as evidenced by the improved learning and memory ability, increased Ach content and ChAT activity, as well as decreased AchE activity in the hippocampus of mice. In total, 390 proteins with fold-change>1.2 or <0.83 and p < 0.05 were identified as significant differentially expressed proteins, of which 110 were significantly up-regulated and 25 were significantly down-regulated between control and model group. By mapping the significantly regulated proteins, we identified five hub proteins: PPP2CA, Gsk3β, PP3CC, PRKACA, and BCL-2 that were associated with dopaminergic synapse and apoptosis signaling pathway, respectively. Western blotting and QPCR demonstrate that the expression levels of these core proteins could be significantly improved by the administration of GPCRAC extracts. These pathways and some of the identified proteins are implicated in AD pathogenesis.

Conclusion: Administration of GPCRAC extracts was effective on alleviating scopolamine-induced cognitive impairment, which might be through modulation of dopaminergic synapse and apoptosis signaling pathway. Consequently, our quantitative proteome data obtained from scopolamine-treated model mice successfully characterized AD-related biological alterations and proposed novel protein biomarkers for AD.

Neuroprotective Effects of Myrtenal in an Experimental Model of Dementia Induced in Rats

There is growing attention on natural substances capable of stimulating the cholinergic system and of exerting antioxidant effects, as potential therapeutic agents in Alzheimer’s disease (AD). The aim of the present study is to evaluate the expected neuroprotective mechanisms of myrtenal (M) in an experimental model of dementia in rats. Dementia was induced in male Wistar rats by scopolamine (Sc) administration (0.1 mg/kg for 8 days and 20.0 mg/kg on day 9). The animals were divided into 5 groups (1) Controls; (2) Sc; (3) Sc + Myrtenal (40 mg/kg), (4) Sc + Galantamine (1 mg/kg); (5) Sc + Lipoic acid (30 mg/kg). Changes in recognition memory and habituation were evaluated via the Novel Object Recognition and Open Field tests. Acetylcholinesterase (AChE) activity, ACh levels, and changes in oxidative status of the brain were measured biochemically. The histological changes in two brain regions—cortex and hippocampus, were evaluated qualitatively and quantitatively. Myrtenal improved recognition memory and habituation, exerted antioxidant effects and significantly increased ACh brain levels. Histologically, the neuroprotective capacity of myrtenal was also confirmed. For the first time, we have demonstrated the neuroprotective potential of myrtenal in an experimental model of dementia. Our study provides proof-of-concept for the testing of myrtenal, in association with standard of care treatments, in patients affected by cognitive decline.

DDA-SKF: Predicting Drug-Disease Associations Using Similarity Kernel Fusion

Drug repositioning provides a promising and efficient strategy to discover potential associations between drugs and diseases. Many systematic computational drug-repositioning methods have been introduced, which are based on various similarities of drugs and diseases. In this work, we proposed a new computational model, DDA-SKF (drug-disease associations prediction using similarity kernels fusion), which can predict novel drug indications by utilizing similarity kernel fusion (SKF) and Laplacian regularized least squares (LapRLS) algorithms. DDA-SKF integrated multiple similarities of drugs and diseases. The prediction performances of DDA-SKF are better, or at least comparable, to all state-of-the-art methods. The DDA-SKF can work without sufficient similarity information between drug indications. This allows us to predict new purpose for orphan drugs. The source code and benchmarking datasets are deposited in a GitHub repository (https://github.com/GCQ2119216031/DDA-SKF).

A Mixture of Ginkgo biloba L. Leaf and Hericium erinaceus (Bull.) Pers. Fruit Extract Attenuates Scopolamine-Induced Memory Impairments in Mice

Alzheimer's disease (AD) is a neurodegenerative disease that is characterized by loss of memory and cognitive impairment via dysfunction of the cholinergic nervous system. In cholinergic dysfunction, it is well known that impaired cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) signaling are major pathological markers and are some of the strategies for the development of AD therapy. Therefore, this study is aimed at evaluating whether a mixture comprising Ginkgo biloba L. leaf (GL) and Hericium erinaceus (Bull.) Pers. (HE) fruit extract (GH mixture) alleviated cognitive impairment induced in a scopolamine-induced model. It was discovered that GH reduced neuronal apoptosis and promoted neuronal survival by activating BDNF signaling in an in vitro assay. In addition, the GH (p.o. 240 mg/kg) oral administration group significantly restored the cognitive deficits of the scopolamine-induced mouse group (i.p. 1.2 mg/kg) in the behavior tests such as Y-maze and novel object recognition task (NORT) tests. This mixture also considerably enhanced cholinergic system function in the mouse brain. Furthermore, GH markedly upregulated the expressed levels of extracellular signal-regulated kinase (ERK), CREB, and BDNF protein levels. These results demonstrated that GH strongly exerted a neuroprotective effect on the scopolamine-induced mouse model, suggesting that an optimized mixture of GL and HE could be used as a good material for developing functional foods to aid in the prevention of neurodegenerative diseases, including AD.

Procognitive activity of nitric oxide inhibitors and donors in animal models

Nitric oxide is a small gaseous molecule that plays important roles in the majority of biological functions. Impairments of NO-related pathways contribute to the majority of neurological disorders, such as Alzheimer's disease (AD), and mental disorders, such as schizophrenia. Cognitive decline is one of the most serious impairments accompanying both AD and schizophrenia. In the present study, the activities of NO donors, slow (spermine NONOate) or fast (DETANONOate) releasers, and selective inhibitor of neuronal nitric oxide synthase N(ω)-propyl-l-arginine (NPLA) were investigated in pharmacological models of schizophrenia and AD. Cognitive impairments were induced by administration of MK-801 or scopolamine and were measured in novel object recognition (NOR) and Y-maze tests. The compounds were investigated at doses of 0.05-0.5 mg/kg. The dose-dependent effectiveness of all the compounds was observed in the NOR test, while only the highest doses of spermine NONOate and NPLA were active in the Y-maze test. DETANONOate was not active in the Y-maze test. The impact of the investigated compounds on motor coordination was tested at doses of 0.5 and 1 mg/kg. Only NPLA at a dose of 1 mg/kg slightly disturbed motor coordination in animals.

The additive memory and healthspan enhancement effects by the combined treatment of mature silkworm powders and Korean angelica extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Silkworm (Bombyx mori) and Korean angelica (KoAg; Angelica gigas Nakai) have been widely used as traditional oriental medicines in Korea, China, and Japan to treat various diseases such as anemia, cold, diabetes, palsy, stroke, etc. Steamed and freeze-dried mature silkworm powder, also known as HongJam (HJ), and extracts of KoAg root (KoAgE) are currently sold in Korea as functional foods to improve memory, cognition, and liver functions. However, the molecular and pharmacological basis for the improvement of brain functions of HJ and KoAgE has not yet been elucidated.

AIM OF STUDY

This study aimed to elucidate the molecular basis underlying the memory-enhancing effects of HJ and KoAgE and determine whether administration of HJ and KoAgE complexes (HJ+KoAgC) has additive memory and healthspan-enhancing effects.

MATERIALS AND METHODS

The MCI mouse models generated by intraperitoneal injection of Scopolamine (Sco-IP) were orally administered with HJ and KoAgE alone or as complexes. Their memory-enhancing effects were examined on spatial, fear-aggravated, and social memories and compared with control or Donepezil (Dp) treatment. The activities of mitochondria complex (MitoCom) I-IV and acetylcholinesterase (AChE) and the amounts of ATP in the mouse brains were examined. The Drosophila model was used to investigate lifespan- and healthspan-promoting effects of HJ+KoAgC.

RESULTS

Administration of HJ+KoAgC produced more memory-enhancing effects than administration of HJ or KoAgE alone or Dp. The increase in MitoCom I-IV activities and ATP amounts and the decrease in AChE activities in the mouse brains were the molecular basis for the memory enhancement. The greatest improvement in memory and mitochondrial function was observed when the mice were administered the 1:0.8 ratio of HJ+KoAgC. Administration of HJ+KoAgC to Drosophila prolonged the lifespan and the healthspan and increased the amounts of ATP.

CONCLUSION

HJ+KoAgC had superior effects on memory improvement and healthspan extension by increasing mitochondrial activities and ATP amounts in treated animal models.

Protective effects of vitamin D on learning and memory deficit induced by scopolamine in male rats: the roles of brain-derived neurotrophic factor and oxidative stress

The beneficial effects of vitamin D (vit D) on central nervous system disorders have been suggested. In the current research, the protective effects of vit D on learning and memory deficit induced by scopolamine, oxidative stress criteria, brain-derived neurotrophic factor (BDNF), and nitric oxide (NO) in the brain were investigated. Rats were divided into five groups, including (1) Control, (2) Scopolamine (2 mg/kg), (3-5) Scopolamine + Vit D (100, 1000, and 10,000 IU/kg) groups. Vit D administrated for 2 weeks and in the third week scopolamine co-administrated with vit D and behavioral tests, including Morris water maze (MWM) and passive avoidance (PA) tests, were carried out. The cortical and hippocampal tissues were analyzed for BDNF, catalase (CAT), and superoxide dismutase (SOD) activities, thiol content, NO metabolites, and malondialdehyde (MDA) concentration. Scopolamine injection significantly impaired rats' performance on the MWM and PA test. It further enhanced the MDA and nitrite level while decreased thiol content and BDNF levels and SOD and CAT activities in the brain. Administration of both 1000 and 10,000 IU/kg vit D improved cognitive outcome in MWM and PA tests. In addition, vit D elevated thiol content, SOD and CAT activities, and BDNF levels, while reduced nitrite and MDA concentration. Vit D also increased the levels of vit D and calcium in the serum. The results demonstrated that vit D has protective effects on scopolamine-associated learning and memory impairment by improving BDNF levels and attenuating NO and brain tissue oxidative damage.

Potential of Caffeine in Alzheimer's Disease-A Review of Experimental Studies

Alzheimer's disease (AD) is the most common type of dementia leading to progressive memory loss and cognitive impairment. Considering that pharmacological treatment options for AD are few and not satisfactory, increasing attention is being paid to dietary components that may affect the development of the disease. Such a dietary component may be caffeine contained in coffee, tea or energy drinks. Although epidemiological data suggest that caffeine intake may counteract the development of cognitive impairment, results of those studies are not conclusive. The aim of the present study is to review the existing experimental studies on the efficacy of caffeine against AD and AD-related cognitive impairment, focusing on the proposed protective mechanisms of action. In conclusion, the reports of studies on experimental AD models generally supported the notion that caffeine may exert some beneficial effects in AD. However, further studies are necessary to elucidate the role of caffeine in the effects of its sources on cognition and possibly AD risk.