p-Coumaric acid mitigates passive avoidance memory and hippocampal synaptic plasticity impairments in aluminum chloride-induced Alzheimer's disease rat model

Mechanistic insights into the potential role of dietary polyphenols and their nanoformulation in the management of Alzheimer's disease

Alzheimer's disease (AD) is a very common neurodegenerative disorder associated with memory loss and a progressive decline in cognitive activity. The two major pathophysiological factors responsible for AD are amyloid plaques (comprising amyloid-beta aggregates) and neurofibrillary tangles (consisting of hyperphosphorylated tau protein). Polyphenols, a class of naturally occurring compounds, are immensely beneficial for the treatment or management of various disorders and illnesses. Naturally occurring sources of polyphenols include plants and plant-based foods, such as fruits, herbs, tea, vegetables, coffee, red wine, and dark chocolate. Polyphenols have unique properties, such as being the major source of anti-oxidants and possessing anti-aging and anti-cancerous properties. Currently, dietary polyphenols have become a potential therapeutic approach for the management of AD, depending on various research findings. Dietary polyphenols can be an effective strategy to tackle multifactorial events that occur with AD. For instance, naturally occurring polyphenols have been reported to exhibit neuroprotection by modulating the Aβ biogenesis pathway in AD. Many nanoformulations have been established to enhance the bioavailability of polyphenols, with nanonization being the most promising. This review comprehensively provides mechanistic insights into the neuroprotective potential of dietary polyphenols in treating AD. It also reviews the usability of dietary polyphenol as nanoformulation for AD treatment.

Underlying mechanisms behind the neuroprotective effect of vanillic acid against diabetes-associated cognitive decline: An in vivo study in a rat model

Hippocampal synaptic dysfunction, oxidative stress, neuroinflammation, and neuronal loss play critical roles in the pathophysiology of diabetes-associated cognitive decline (DACD). The study aimed to investigate the effects of vanillic acid (VA), a phenolic compound, against DACD and explore the potential underlying mechanisms. Following confirmation of diabetes, rats were treated with VA (50 mg/kg/day; P.O.) or insulin (6 IU/rat/day; S.C.) for 8 consecutive weeks. The cognitive performance of the rats was evaluated using passive-avoidance and water-maze tasks. Long-term potentiation (LTP) was induced at hippocampal dentate gyrus (DG) synapses in response to high-frequency stimulation (HFS) applied to the perforant pathway (PP) to evaluate synaptic plasticity. Oxidative stress factors, inflammatory markers, and histological changes were evaluated in the rat hippocampus. This study showed that streptozotocin (STZ)-induced diabetes caused cognitive decline that was associated with inhibition of LTP induction, suppression of enzymatic antioxidant activities, enhanced lipid peroxidation, elevated levels of inflammatory proteins, and neuronal loss. Interestingly, chronic treatment with VA alleviated blood glucose levels, improved cognitive decline, ameliorated LTP impairment, modulated oxidative-antioxidative status, inhibited inflammatory response, and prevented neuronal loss in diabetic rats at a level comparable to insulin therapy. The results suggest that the antihyperglycemic, antioxidative, anti-inflammatory, and neuroplastic properties of VA may be the mechanisms behind its neuroprotective effect against DACD.

A supercritical fluid co-extract of turmeric powder and dried coconut shreds shows neuroprotection against AlCl3-induced Alzheimer's disease in rats through nose to brain delivery

This study was aimed at investigating the neuroprotective potential of a co-extract obtained by supercritical fluid extraction (SFE) of turmeric powder and dried coconut shreds against aluminium chloride (AlCl3)-induced Alzheimer's disease (AD) in male Wistar rats. Fifty animals were allocated to five groups, which received saline (vehicle control, group 1), a combination of saline and aluminium chloride (AlCl3) (disease control, group 2), coconut oil (COO) (SFE extracted, treatment group 3), turmeric oleoresin (Cur) (SFE extracted, treatment group 4) and SFE co-extract of turmeric powder and coconut shreds (CurCOO) (treatment group 5). Animals were subjected to behavioural evaluation. In addition, the hippocampal section of the brain from all groups was subjected to biochemical, molecular and histopathological evaluations. The results showed CurCOO administered intranasally improved cognitive abilities, reversed histological alterations in the brain, reduced hippocampus inflammation studied through proinflammatory cytokine markers like TNF-α and IL-6 as compared to the disease control group. The impact of CurCOO on preventive neurodegeneration was also observed through a reduction in protein transcription factor NF-kB in the treated group 5 as compared to a disease control group. The effect of intranasal delivery of CurCOO on the neurons responsible for memory consolidation was evident from low acetylcholinesterase (AChE) enzyme activity in the treated groups with respect to AlCl3 induced group. Summarily, the results demonstrated intranasal delivery of CurCOO to show better efficacy than Cur and COO in preventing neurodegeneration associated with AlCl3 induced Alzheimer's disease.

Mediterranean Shrub Species as a Source of Biomolecules against Neurodegenerative Diseases

Neurodegenerative diseases are associated with oxidative stress, due to an imbalance in the oxidation-reduction reactions at the cellular level. Various treatments are available to treat these diseases, although they often do not cure them and have many adverse effects. Therefore, it is necessary to find complementary and/or alternative drugs that replace current treatments with fewer side effects. It has been demonstrated that natural products derived from plants, specifically phenolic compounds, have a great capacity to suppress oxidative stress and neutralize free radicals thus, they may be used as alternative alternative pharmacological treatments for pathological conditions associated with an increase in oxidative stress. The plant species that dominate the Mediterranean ecosystems are characterized by having a wide variety of phenolic compound content. Therefore, these species might be important sources of neuroprotective biomolecules. To evaluate this potential, 24 typical plant species of the Mediterranean ecosystems were selected, identifying the most important compounds present in them. This set of plant species provides a total of 403 different compounds. Of these compounds, 35.7% are phenolic acids and 55.6% are flavonoids. The most relevant of these compounds are gallic, vanillic, caffeic, chlorogenic, p-coumaric, and ferulic acids, apigenin, kaempferol, myricitrin, quercetin, isoquercetin, quercetrin, rutin, catechin and epicatechin, which are widely distributed among the analyzed plant species (in over 10 species) and which have been involved in the literature in the prevention of different neurodegenerative pathologies. It is also important to mention that three of these plant species, Pistacea lentiscus, Lavandula stoechas and Thymus vulgaris, have most of the described compounds with protective properties against neurodegenerative diseases. The present work shows that the plant species that dominate the studied geographic area can provide an important source of phenolic compounds for the pharmacological and biotechnological industry to prepare extracts or isolated compounds for therapy against neurodegenerative diseases.

p-Coumaric acid attenuates the effects of Aβ42 in vitro and in a Drosophila Alzheimer's disease model

Alzheimer's disease (AD) is the most common neurodegenerative condition in civilizations worldwide. The distinctive occurrence of amyloid-beta (Aβ) accumulation into insoluble fibrils is part of the disease pathophysiology with Aβ42 being the most toxic and aggressive Aβ species. The polyphenol, p-Coumaric acid (pCA), has been known to boost a number of therapeutic benefits. Here, pCA's potential to counteract the negative effects of Aβ42 was investigated. First, pCA was confirmed to reduce Aβ42 fibrillation using an in vitro activity assay. The compound was next examined on Aβ42-exposed PC12 neuronal cells and was found to significantly decrease Aβ42-induced cell mortality. pCA was then examined using an AD Drosophila melanogaster model. Feeding of pCA partially reversed the rough eye phenotype, significantly lengthened AD Drosophila's lifespan, and significantly enhanced the majority of the AD Drosophila's mobility in a sex-dependent manner. The findings of this study suggest that pCA may have therapeutic benefits for AD.

Codium fragile Suppresses PM2.5-Induced Cognitive Dysfunction by Regulating Gut-Brain Axis via TLR-4/MyD88 Pathway

This study was conducted to evaluate the cognitive dysfunction improvement effect of aqueous extract of Codium fragile (AECF) by regulating the imbalance of the gut-brain axis in chronic particulate matter (PM)2.5-exposed mice. The physiological compounds of AECF were identified as hexadecanamide, oleamide, octadecanamide, stearidonic acid, and linolenic acid by the ultra-performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC Q-TOF MSE) analysis. To evaluate the effect of PM2.5 on the antioxidant system, superoxide dismutase (SOD) contents, reduced glutathione (GSH) contents, and malondialdehyde (MDA) contents were measured in colon and brain tissues. AECF significantly ameliorated the imbalance of the antioxidant systems. Also, AECF improved intestinal myeloperoxidase (MPO) activity, the abundance of the gut microbiome, short-chain fatty acids (SCFAs) contents, and tight junction protein expression against PM2.5-induced damage. In addition, AECF prevented PM2.5-induced inflammatory and apoptotic expression via the toll-like receptor-4 (TLR-4)/myeloid differentiation primary response 88 (MyD88) pathway in colon and brain tissues. Additionally, AECF enhanced the mitochondrial function, including the mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) contents in brain tissues. Furthermore, AECF regulated the cholinergic system, such as acetylcholine (ACh) contents, acetylcholinesterase (AChE) activity, and protein expression levels of AChE and choline acetyltransferase (ChAT) in brain tissues. To evaluate the effect of cognitive dysfunction caused by PM2.5-induced intestinal dysfunction, behavior tests such as Y-maze, passive avoidance, and Morris water maze tests were performed. From the results of the behavior tests, AECF ameliorated spatial learning and memory, short-term memory, and long-term learning and memory function. This study confirmed that AECF reduced PM2.5-induced cognitive dysfunction by regulating gut microbiome and inflammation, apoptosis, and mitochondrial function by enhancing the gut-brain axis. Based on these results, this study suggests that AECF, which contains fatty acid amides, might be a potential material for ameliorating PM2.5-induced cognitive dysfunction via gut-brain axis improvement.

Apitherapy in Post-Ischemic Brain Neurodegeneration of Alzheimer's Disease Proteinopathy: Focus on Honey and Its Flavonoids and Phenolic Acids

Neurodegeneration of the brain after ischemia is a major cause of severe, long-term disability, dementia, and mortality, which is a global problem. These phenomena are attributed to excitotoxicity, changes in the blood-brain barrier, neuroinflammation, oxidative stress, vasoconstriction, cerebral amyloid angiopathy, amyloid plaques, neurofibrillary tangles, and ultimately neuronal death. In addition, genetic factors such as post-ischemic changes in genetic programming in the expression of amyloid protein precursor, β-secretase, presenilin-1 and -2, and tau protein play an important role in the irreversible progression of post-ischemic neurodegeneration. Since current treatment is aimed at preventing symptoms such as dementia and disability, the search for causative therapy that would be helpful in preventing and treating post-ischemic neurodegeneration of Alzheimer's disease proteinopathy is ongoing. Numerous studies have shown that the high contents of flavonoids and phenolic acids in honey have antioxidant, anti-inflammatory, anti-apoptotic, anti-amyloid, anti-tau protein, anticholinesterase, serotonergic, and AMPAK activities, influencing signal transmission and neuroprotective effects. Notably, in many preclinical studies, flavonoids and phenolic acids, the main components of honey, were also effective when administered after ischemia, suggesting their possible use in promoting recovery in stroke patients. This review provides new insight into honey's potential to prevent brain ischemia as well as to ameliorate damage in advanced post-ischemic brain neurodegeneration.

Functionalization of Silica Nanoparticles by 5-Chloro-8-quinolinol as a New Nanocomposite for the Efficient Removal and Preconcentration of Al3+ Ions from Water Samples

In this work, silica nanoparticles were modified by 5-chloro-8-quinolinol as a new nanocomposite for the efficient elimination and preconcentration of Al³⁺ ions from several water sources. The fabricated composite was characterized utilizing XRD, SEM, FT-IR, TEM, CHN elemental analyzer, and N₂ adsorption/desorption analyzer. The XRD demonstrated the existence of a wide peak at 2θ = 30°. Also, all the peaks of silica were severely reduced, which confirms the success of loading the 5-chloro-8-quinolinol on the surface of the silica. The SEM and TEM images demonstrated that the composite resembled cotton, and this confirms that 5-chloro-8-quinolinol was successfully loaded on the silica surface. The specific surface area, the average pore size, and the total pore volume of the synthesized composite are 80.53 m²/g, 3.26 nm, and 0.185 cc/g, respectively. In addition, the greatest uptake capacity of the synthesized composite toward aluminum ions is 95.06 mg/g. The results indicated that the adsorption of aluminum ions onto the silica/5-chloro-8-quinolinol composite follows the Langmuir isotherm and pseudo-second-order model. Moreover, the adsorption of aluminum ions by the silica/5-chloro-8-quinolinol composite is spontaneous, chemical, and thermodynamically favorable. The values of % recovery were more than 97%, whereas the values of % RSD were less than 3.5%. Hence, this confirms the effectiveness of the proposed method in the determination of aluminum ions in real water samples.

The Protective Effects of Policosanol on Learning and Memory Impairments in a Male Rat Model of Alzheimer's Disease

Alzheimer's disease (AD), the most common form of dementia, is characterized by a progressive decline in cognitive performance and memory formation. The present study was designed to investigate the effect of policosanol (PCO) on cognitive function, oxidative-antioxidative status, and amyloid-beta (Aβ) plaque formation in an AD rat model induced by intracerebroventricular (ICV) injection of Aβ_1-40. Healthy adult male Wistar rats were randomly divided into seven groups: control, sham (5 μL, ICV injection of phosphate-buffered saline), AD model (5 μL, ICV injection of Aβ), acacia gum (50 mg/kg, 8 weeks, gavage), PCO (50 mg/kg, 8 weeks, gavage), AD + acacia gum (50 mg/kg, 8 weeks, gavage), and AD + PCO (50 mg/kg, 8 weeks, gavage). During the ninth and tenth weeks of the study, the cognitive function of the rats was assessed by commonly used behavioral paradigms. Subsequently, oxidative-antioxidative status was examined in the serum. Moreover, compact Aβ plaques were detected by Congo red staining. The results showed that injection of Aβ impaired recognition memory in the novel object recognition test, reduced the spatial cognitive ability in the Morris water maze, and alleviated retention and recall capability in the passive avoidance task. Additionally, injection of Aβ resulted in increased total oxidant status, decreased total antioxidant capacity, and enhanced Aβ plaque formation in the rats. Intriguingly, PCO treatment improved all the above-mentioned neuropathological changes in the Aβ-induced AD rats. The results suggest that PCO improves Aβ-induced cognitive decline, possibly through modulation of oxidative-antioxidative status and inhibition of Aβ plaque formation.

Geraniol improves passive avoidance memory and hippocampal synaptic plasticity deficits in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is the most progressive and irreversible neurodegenerative disease that leads to synaptic loss and cognitive decline. The present study was designed to evaluate the effects of geraniol (GR), a valuable acyclic monoterpene alcohol, with protective and therapeutic effects, on passive avoidance memory, hippocampal synaptic plasticity, and amyloid-beta (Aβ) plaques formation in an AD rat model induced by intracerebroventricular (ICV) microinjection of Aβ_1-40. Seventy male Wistar rats were randomly into sham, control, control-GR (100 mg/kg; P.O. (orally), AD, GR-AD (100 mg/kg; P.O.; pretreatment), AD-GR (100 mg/kg; P.O.; treatment), and GR-AD-GR (100 mg/kg; P.O.; pretreatment & treatment). Administration of GR was continued for four consecutive weeks. Training for the passive avoidance test was carried out on the 36^th day and a memory retention test was performed 24 h later. On day 38, hippocampal synaptic plasticity (long-term potentiation; LTP) was recorded in perforant path-dentate gyrus (PP-DG) synapses to assess field excitatory postsynaptic potentials (fEPSPs) slope and population spike (PS) amplitude. Subsequently, Aβ plaques were identified in the hippocampus by Congo red staining. The results showed that Aβ microinjection increased passive avoidance memory impairment, suppressed of hippocampal LTP induction, and enhanced of Aβ plaque formation in the hippocampus. Interestingly, oral administration of GR improved passive avoidance memory deficit, ameliorated hippocampal LTP impairment, and reduced Aβ plaque accumulation in the Aβ-infused rats. The results suggest that GR mitigates Aβ-induced passive avoidance memory impairment, possibly through alleviation of hippocampal synaptic dysfunction and inhibition of Aβ plaque formation.

Policosanol protects against Alzheimer's disease-associated spatial cognitive decline in male rats: possible involved mechanisms

RATIONALE

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by cognitive decline and synaptic failure.

OBJECTIVE

The present study was designed to explore the possible protective effects of policosanol (PCO) on spatial cognitive capacity, long-term potentiation (LTP) induction, oxidant/antioxidant status, and Aβ plaques formation in an AD rat model induced by intracerebroventricular (ICV) injection of Aβ_1-40.

METHODS

Healthy adult male Wistar rats were randomly divided into control, sham (ICV injection of 5 µl phosphate-buffered saline), AG (50 mg/kg; P.O., as PCO vehicle), PCO (50 mg/kg; P.O.), AD model (ICV injection of 5 µl Aβ), AD + AG (50 mg/kg; P.O.), and AD + PCO (50 mg/kg; P.O.). Treatments were performed for eight consecutive weeks. At the end of the treatment course, spatial learning and memory functions, hippocampal long-term potentiation (LTP) induction, malondialdehyde (MDA), and total thiol group (TTG) levels, as well as the formation of Aβ plaques, were examined.

RESULTS

The results showed that injection of Aβ reduced spatial learning and memory abilities in the Barnes maze test, which was accompanied by decreases in field excitatory postsynaptic potential (fEPSP) slope, population spike (PS) amplitude, and TTG level and increases in Aβ plaque accumulation and MDA content. In contrast, PCO treatment improved all the above-mentioned changes in the Aβ-infused rats.

CONCLUSIONS

The results suggest that amelioration of hippocampal synaptic plasticity impairment, modulation of oxidant/antioxidant status, and inhibition of Aβ plaque formation by PCO may be the mechanisms behind its protective effect against AD-associated spatial cognitive decline.

Honey and Alzheimer's Disease-Current Understanding and Future Prospects

Alzheimer's disease (AD), a leading cause of dementia, has been a global concern. AD is associated with the involvement of the central nervous system that causes the characteristic impaired memory, cognitive deficits, and behavioral abnormalities. These abnormalities caused by AD is known to be attributed by extracellular aggregates of amyloid beta plaques and intracellular neurofibrillary tangles. Additionally, genetic factors such as abnormality in the expression of APOE, APP, BACE1, PSEN-1, and PSEN-2 play a role in the disease. As the current treatment aims to treat the symptoms and to slow the disease progression, there has been a continuous search for new nutraceutical agent or medicine to help prevent and cure AD pathology. In this quest, honey has emerged as a powerful nootropic agent. Numerous studies have demonstrated that the high flavonoids and phenolic acids content in honey exerts its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes the effect of main flavonoid compounds found in honey on the physiological functioning of the central nervous system, and the effect of honey intake on memory and cognition in various animal model. This review provides a new insight on the potential of honey to prevent AD pathology, as well as to ameliorate the damage in the developed AD.

The neuroprotective effect of ginsenoside Rb1 on the cerebral cortex changes induced by aluminium chloride in a mouse model of Alzheimer's disease: A histological, immunohistochemical, and biochemical study

Alzheimer's disease (AD) is one of the most common types of dementia among neurodegenerative disorders characterized by attention deficits and memory loss. Panax ginseng is a traditional Chinese herbal remedy that has been employed for millennia to manage dementia linked with aging and memory impairment. Ginsenoside Rb1 is one of Panax ginseng's most abundant components. The present work evaluated the neuroprotective effects of ginsenoside Rb1 on the cerebral cortex of AlCl₃-induced AD in adult male albino mice. Forty male mice were alienated arbitrarily into; control group, ginsenoside Rb1 group (70 mg/kg/day), AlCl₃ group (50 mg/kg/day), and ginsenoside Rb1-AlCl₃ group that received ginsenoside Rb1 one hour before AlCl₃. Oxidative stress parameters, Amyloid β (Aβ) and phosphorylated tau protein, and acetylcholine esterase (AChE) activity were measured. Cerebral cortex sections were evaluated histologically by light microscopic examination and immunohistochemistry. AlCl₃-induced memory impairment, Aβ and phosphorylated tau protein accumulation, and AChE elevation. Moreover, histopathological alterations in the cerebral cortex were reported in the form of irregular shrunken neurons and the surrounding neuropil showed vacuolation. Some neurons appeared with darkly stained nuclei, others had faintly stained ones. The synaptophysin expression was significantly decreased, while the expression of cleaved caspase-3, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba-1) were significantly elevated. It's interesting to note that these changes were attenuated in mice pretreated with ginsenoside Rb1. Collected data indicated that ginsenoside Rb1 showed a potential neuroprotective effect against cerebral cortex changes caused by AlCl₃ via suppression of Amyloid β and phosphorylated tau protein formation, oxidative stress correction, anti-apoptotic effect, and by minimizing gliosis.