Alzheimer's Disease Rats Research Articles

40 Hz light preserves synaptic plasticity and mitochondrial function in Alzheimer’s disease model

Alzheimer’s disease (AD) is the most prevalent type of dementia. Its causes are not fully understood, but it is now known that factors like mitochondrial dysfunction, oxidative stress, and compromised ion channels contribute to its onset and progression. Flickering light therapy has shown promise in AD treatment, though its mechanisms remain unclear. In this study, we used a rat model of streptozotocin (STZ)-induced AD to evaluate the effects of 40 Hz flickering light therapy. Rats received intracerebroventricular (ICV) STZ injections, and 7 days after, they were exposed to 40 Hz flickering light for 15 min daily over seven days. Cognitive and memory functions were assessed using Morris water maze, novel object recognition, and passive avoidance tests. STZ-induced AD rats exhibited cognitive decline, elevated reactive oxygen species, amyloid beta accumulation, decreased serotonin and dopamine levels, and impaired mitochondrial function. However, light therapy prevented these effects, preserving cognitive function and synaptic plasticity. Additionally, flickering light restored mitochondrial metabolites and normalized ATP-insensitive mitochondrial calcium-sensitive potassium (mitoBKCa) channel activity, which was otherwise downregulated in AD rats. Our findings suggest that 40 Hz flickering light therapy could be a promising treatment for neurodegenerative disorders like AD by preserving synaptic and mitochondrial function.

Adipose-Derived Mesenchymal Stem Cell (AD-MSC)-Like Cells Restore Nestin Expression and Reduce Amyloid Plaques in Aluminum Chloride (AlCl3)-Driven Alzheimer's Rat Models

Adipose-Derived Mesenchymal Stem Cell (AD-MSC)-Like Cells Restore Nestin Expression and Reduce Amyloid Plaques in Aluminum Chloride (AlCl3)-Driven Alzheimer's Rat Models

Efficacy and Mechanism of Schisandra chinensis Fructus Water Extract in Alzheimer's Disease: Insights from Network Pharmacology and Validation in an Amyloid-β Infused Animal Model.

Schisandra chinensis Fructus (SCF) is a traditional medicinal herb containing lignans that improves glucose metabolism by mitigating insulin resistance. We aimed to investigate the therapeutic potential and action mechanism of SCF for Alzheimer's disease (AD) using a network pharmacology analysis, followed by experimental validation in an AD rat model. The biological activities of SCF's bioactive compounds were assessed through a network pharmacology analysis. An AD rat model was generated by infusing amyloid-β peptide (Aβ) (25-35) into the hippocampus to induce Aβ accumulation. The AD rats were fed either 0.5% dextrin (AD-Con) or 0.5% SCF (AD-SCF group) in a high-fat diet for seven weeks. The rats in the normal/control group received an Aβ (35-25) infusion (no Aβ deposition) and were fed a control diet (Normal-C). Aβ deposition, memory function, inflammation, and glucose/lipid metabolism were evaluated. The network analysis revealed significant intersections between AD-related targets and bioactive SCF compounds, like gomisin A, schisandrin, and longikaurin A. Key AD genes prostaglandin-endoperoxide synthase-2 (PTGS2, cyclooxygenase-2) and acetylcholinesterase (AChE) were linked to SCF compounds. In the rats with AD induced by bilaterally infusing amyloid-β (25-35) into the hippocampus, the 0.5% SCF intake mitigated hippocampal amyloid-β deposition, neuroinflammation, memory deficits, and dysregulated glucose and lipid metabolism versus the AD controls. SCF reduced hippocampal AChE activity, inflammatory cytokine expression related to PTGS2, and malondialdehyde contents and preserved neuronal cell survival-related factors such as brain-derived neurotrophic factor and ciliary neurotrophic factor similar to normal rats. The neuroprotective effects validated the network analysis findings. SCF could be a potential AD therapeutic agent by activating the parasympathetic nervous system to reduce hippocampal oxidative stress and inflammation, warranting further clinical investigations of its efficacy.

Effect of Nattokinase in D-galactose- and Aluminum Chloride-induced Alzheimer's Disease Model of Rat.

Alzheimer's disease (AD) is the most common form of dementia worldwide. Nattokinase is a serine protease extracellularly produced by natto, a fermented product of Bacillus subtilis var. natto. In this study, we investigated the therapeutic effects of nattokinase in a rat model of AD induced by aluminum and D-galactose. Forty Wistar rats were randomly divided into four groups: normal, vehicle, and orally administered nattokinase (NK65 and NK130 groups). Except for the normal group, all groups were treated with AlCl3 and D-galactose for 10 weeks. The NK65 and NK130 groups additionally received 65 mg/kg/day and 130 mg/kg/day nattokinase, respectively. We analyzed β-amyloid levels in the cerebrospinal fluid (CSF), and the spatial reference test was evaluated using the Morris water maze test. After the Morris water maze test, rats of all groups were subjected to micro-computed tomography (μCT) to assess constructional changes in the brain. Aluminum concentration and β-amyloid levels were analyzed by histochemical staining in all brain tissues. Oral administration of nattokinase in the AD rat model increased free-form β-amyloid levels in the CSF and improved aluminum and amyloid plaque accumulation in the brain. Brain μCT images showed enhanced brain volume with fewer constructional changes after treatment with nattokinase. In the behavioral tests, both the escape latency time in the spatial reference test and the time taken to cross the platform area in the spatial probe test improved partially. The results suggest that nattokinase has potential therapeutic applications in the treatment of AD.

Melatonin and Hydrogen Sulfide ameliorates cognitive impairments in Alzheimer's disease rat model exposed to chronic mild stress via attenuation of neuroinflamation and inhibition of oxidative stress: Potential role of BDNF

Melatonin and Hydrogen Sulfide ameliorates cognitive impairments in Alzheimer's disease rat model exposed to chronic mild stress via attenuation of neuroinflamation and inhibition of oxidative stress: Potential role of BDNF

Down regulation of the c-Fos/MAP kinase signaling pathway during learning memory processes coincides with low GnRH levels in aluminum chloride-induced Alzheimer's male rats.

Aluminum chloride (Al) is associated with Alzheimer's disease (AD) and reproductive disorders. But the relationship between gonadotropin-releasing hormone (GnRH) and c-Fos levels, the end product of MAP-kinase signaling, in AD is unknown, so we aimed to investigate this relationship. We exposed rats to Al dissolved in drinking water (10 and 50mg/kg) for two and four weeks. The control group received only drinking water. At the end, the blood sample was collected under deep anesthesia and the brain was dissected on ice, and the testicular tissue was fixed in formalin. Amyloid beta (βA) plaques in brain regions and the number of CA1 neurons were evaluated by Congo red staining and cresyl violet staining. Activation of neuronal nitric oxide synthase (nNOS) was studied using NADPH-diaphorase. The levels of c-Fos and testosterone receptors in the target area were examined immunohistochemically. Brain GnRH levels were determined by blotting, and serum levels of gonadotropins and steroids were measured by enzyme-linked immunosorbent assay (ELISA). All data were analyzed using analysis of variance (ANOVA) at α = 0.05 level. The accumulation of βA plaque was observed along with a decrease in the number of CA1 pyramidal neurons and a significant decrease in the levels of c-Fos and GnRH in the brains of rats receiving Al, which was aligned with a significant decrease in serum levels of testosterone and LH. This study, for the first time, showed a link between dementia and a concomitant decrease in brain GnRH and c-Fos levels.

A tailored phytosomes based nose-to-brain drug delivery strategy: Silver bullet for Alzheimer's disease

With the aging of the population, the incidence of Alzheimer's disease (AD) has increased dramatically, causing severe medical, care, and economic burdens on society and families. The efficacy of rivastigmine hydrogen tartrate (RHT), the first-line clinical treatment, is severely limited by the complex and multiple pathogenesis of AD and low brain bioavailability caused by the blood-brain barrier (BBB). Confronting such two bottlenecks, the development of multi-target agents encapsulated BBB-bypassing drug delivery systems offer tremendous therapeutics possibilities for AD. In this study, a tailored phytosomes based nose-to-brain drug delivery system with appropriate plume was successfully designed and developed. On the one hand, Ginseng RG3-based phytosomes loaded with RHT was designed for the co-delivery of GRg3 and RHT, achieving the multi-target pharmacology for AD treatment. On the other hand, a tailored nose-to-brain drug delivery system was established for the satisfactory nose-to-brain delivery efficiency, avoiding the obstacle of BBB through bypassing it. In the pharmacodynamic study based on AD rat model, GRg3@RHT exhibited obviously synergic effect, effectively break the vicious cycle of AD progression, ultimately markedly ameliorating learning and memory ability as well as behavioral dysfunctions, and delaying the neurodegenerative process associated with AD. In addition, the strong correlation of viscosity-droplet size-plume geometry-olfactory deposition was also established, and further proved by the in vivo pharmacokinetic study, which is proposed to provide evidence to enhance nose-to-brain delivery efficiency. This study is anticipated to provide novel insights into AD treatment strategies while offering innovative ideas for drug delivery approaches targeting nervous system disorders.

Anticholinesterase, Antioxidative and Neuroprotective Effects of Hydroethanolic Extracts of Guiera Senegalensis J. F. Gmel. Leaves on Scopolamine Induced Alzheimer’s Disease in Wistar Rat Models

Background: Medicinal plants like Guiera senegalensis J. F. Gmel. (GS) have gained attention for their potential neuroprotective effects due to their rich composition of bioactive compounds, including flavonoids and polyphenolic acids. While previous studies have highlighted the antioxidant, anti-inflammatory, and neuroplasticity-enhancing properties of GS extract, its efficacy in mitigating dementia-related pathology remains to be fully understood. Objectives: This study aimed to investigate the neuroprotective effects of hydroethanolic GS extract against scopolamine (Sco)-induced dementia in Wistar rats, focusing on its impact on cholinergic function, oxidative stress, neuroinflammation, neurodegeneration, and memory impairment. Methods: Fresh leaves were processed for extraction using standard methods. Antioxidant activity was evaluated using FRAP and DPPH assays. Adult male Wistar rats were used for behavioral tests (Y-maze, NOR, MWM) and biochemical analyses, including ELISA for cholinergic activity, oxidative stress markers (Aβ1-42, phosphorylated Tau), pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IFN-γ), GFAP, BDNF, and IL-10. Brain tissues underwent histopathological examination. Data were analyzed using GraphPad Prism software. Results: The study assessed the antioxidant potential of GS extract and found that it significantly scavenged DPPH radicals (70.29%) and reduced Fe3+ (49.69%). Behavioral tests showed that GS extract (100 - 400 mg/kg) improved spatial memory and learning in Sco-treated rats. Y-maze results indicated increased spontaneous alternation with GS extract (P < 0.01). NOR and MWM tests showed improved memory and learning, with GS extract-treated rats spending more time in the target quadrant. Biochemical analysis revealed that GS extract increased acetylcholine (ACh), Superoxide Dismutase (SOD), Catalase (CAT), Glutathione (GSH), IL-10, and BDNF levels, while decreasing acetylcholinesterase (AChE), malondialdehyde (MDA), nitrite, Aβ1-42, phosphorylated Tau, IL-1β, TNF-α, IL-6, IFN-γ, and GFAP levels in the hippocampus. Histological analysis confirmed restored hippocampal tissue architecture in AD rats treated with GS extract. Conclusions: Our findings suggest that GS modulates cholinergic, antioxidant, anti-inflammatory, and neuroplasticity pathways, exerting beneficial effects on cognitive functions and biochemical markers associated with Alzheimer's disease (AD) pathology. These results indicate the potential of GS as a neuroprotective agent for the treatment of AD.

8596 Brain Type 3 Deiodinase Is Induced in Two Disease Models That Lead to Cognitive Impairment: Liver Dysfunction and Alzheimer Disease

Abstract Disclosure: S. Wajner: None. T. Oliveira: None. M. Dreher: None. R. Ribeiro: None. C. Gonçalves: None. M.R. Alveres-da-Silva: None. Thyroid hormone is the leading regulator of cell energy production in most tissues, mainly the brain. While the activation process of T4 into T3 depends on D1 and D2 deiodinases, type 3 is the main enzyme that inactivates T3. Several mechanisms, among them oxidative stress, led by disease, imbalances and induces D3, diminishing T3 levels. The response of D3 in the brain in the context of different disease models has yet to be studied. Here we evaluated D3 induction in the brain in two animal disease models, one systemic and the other local. Methodology: To the metabolic dysfunction-associated steatosis liver disease model Male/adult Sprague Dawley rats (n=20) were assigned to control group (standard diet-2.93kcal/g) or high-fat-diet group (CDHF-4.3kcal/g). In the streptozotocin-induced (STZ) Alzheimer's model Adult Wistar rats (n=16) were allocated to the control group (5uL of citrate) or 5uL of streptozotocin. Sham animals were used as controls. D3 expression, oxidative stress parameters, endoplasmic stress and mitochondrial amount measured in the brain. Levels of D3 increased in the brain (∼30% in each group, P<0.0001) in both MASLD and STZ groups. Cerebral tissue from both groups had augmented carbonyl levels (P<0.001) and reduced sulfhydryl (P<0.001). Glutathione was diminished. Antioxidant defenses endoplasmic reticulum function and mitochondrial concentration were altered (P=0.001). The augmented T3 inactivation by D3 dysfunction in brain due to oxidative stress disrupts ER-mitochondrial contact interaction, changing the function of organelles in both brain disease models, shedding light to new mechanisms of action of thyroid hormone in severe brain disease. Presentation: 6/3/2024

Ameliorative effects of Akkermansia muciniphila on anxiety-like behavior and cognitive deficits in a rat model of Alzheimer’s disease

Alzheimer’s Disease (AD) is the primary neurodegenerative disorder in the elderly, lacking a definitive treatment. The gut microbiota influences the gut-brain axis by aiding in hypothalamic–pituitary–adrenal (HPA) axis development and neuromodulator production. Research links AD and gut microbiota, suggesting gut microbiota regulation could be a therapeutic approach for AD. This study explores Akkermansia muciniphila’s impact on preventing AD. This research investigates the effect of A. muciniphila consumption (1 × 109 CFU) on tau protein-induced AD rats compared to a control group. Rats were divided into four groups: sham, sham + Akk, AD (tau-induced rats), and AD + Akk (tau-induced rats treated with A. muciniphila). A. muciniphila gavage lasted five weeks. Rats underwent qRT-PCR analysis to assess mRNA expression of pro-inflammatory factors (TNF-α, IL-6, IL-1β, IFN-γ) in the hippocampus. Behavioral tests included Morris Water Maze (MWM), Passive Avoidance Memory Test (Shuttle box), Elevated Plus Maze (EPM), and marble burying. After five weeks of A. muciniphila treatment, anxiety-like behavior significantly decreased. The AD group receiving A. muciniphila showed improved spatial and recognition memory compared to the AD group. Pro-inflammatory cytokine levels (TNF-α, IL-1β, IL-6, IFN-γ) decreased. A. muciniphila effectively reduces cognitive impairments and anxiety-related behavior, showing promise as an AD therapeutic by influencing the gut-brain axis.

Melatonin Supplementation Alleviates Impaired Spatial Memory by Influencing Aβ1-42 Metabolism via γ-Secretase in the icvAβ1-42 Rat Model with Pinealectomy

In the search for Alzheimer’s disease (AD) therapies, most animal models focus on familial AD, which accounts for a small fraction of cases. The majority of AD cases arise from stress factors, such as oxidative stress, leading to neurological changes (sporadic AD). Early in AD progression, dysfunction in γ-secretase causes the formation of insoluble Aβ1-42 peptides, which aggregate into senile plaques, triggering neurodegeneration, cognitive decline, and circadian rhythm disturbances. To better model sporadic AD, we used a new AD rat model induced by intracerebroventricular administration of Aβ1-42 oligomers (icvAβ1-42) combined with melatonin deficiency via pinealectomy (pin). We validated this model by assessing spatial memory using the radial arm maze test and measuring Aβ1-42 and γ-secretase levels in the frontal cortex and hippocampus with ELISA. The icvAβ1-42 + pin model experienced impaired spatial memory and increased Aβ1-42 and γ-secretase levels in the frontal cortex and hippocampus, effects not seen with either icvAβ1-42 or the pin alone. Chronic melatonin treatment reversed memory deficits and reduced Aβ1-42 and γ-secretase levels in both structures. Our findings suggest that our icvAβ1-42 + pin model is extremely valuable for future AD research.

Zeaxanthin and Lutein Ameliorate Alzheimer's Disease-like Pathology: Modulation of Insulin Resistance, Neuroinflammation, and Acetylcholinesterase Activity in an Amyloid-β Rat Model.

Alzheimer's disease (AD) is characterized by impaired insulin/insulin-like growth factor-1 signaling in the hippocampus. Zeaxanthin and lutein, known for their antioxidant and anti-inflammatory properties, have been reported to protect against brain damage and cognitive decline. However, their mechanisms related to insulin signaling in AD remain unclear. This study investigated the efficacy and mechanisms of zeaxanthin, lutein, and resveratrol in modulating an AD-like pathology in an amyloid-β rat model. Rats were administered hippocampal infusions of 3.6 nmol/day amyloid-β (Aβ)(25-35) for 14 days to induce AD-like memory deficits (AD-CON). Normal control rats received Aβ(35-25) (Normal-CON). All rats had a high-fat diet. Daily, AD rats consumed 200 mg/kg body weight of zeaxanthin (AD-ZXT), lutein (AD-LTN), and resveratrol (AD-RVT; positive-control) or resistant dextrin as a placebo (AD-CON) for eight weeks. The AD-CON rats exhibited a higher Aβ deposition, attenuated hippocampal insulin signaling (reduced phosphorylation of protein kinase B [pAkt] and glycogen synthase kinase-3β [pGSK-3β]), increased neuroinflammation, elevated acetylcholinesterase activity, and memory deficits compared to the Normal-CON group. They also showed systemic insulin resistance and high hepatic glucose output. Zeaxanthin and lutein prevented memory impairment more effectively than the positive-control resveratrol by suppressing acetylcholinesterase activity, lipid peroxidation, and pro-inflammatory cytokines (TNF-α, IL-1β). They also potentiated hippocampal insulin signaling and increased brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CTNF) mRNA expression to levels comparable to the Normal-CON rats. Additionally, zeaxanthin and lutein improved glucose disposal, reduced hepatic glucose output, and normalized insulin secretion patterns. In conclusion, zeaxanthin and lutein supplementation at doses equivalent to 1.5-2.0 g daily in humans may have practical implications for preventing or slowing human AD progression by reducing neuroinflammation and maintaining systemic and central glucose homeostasis, showing promise even when compared to the established neuroprotective compound resveratrol. However, further clinical trials are needed to evaluate their efficacy and safety in human populations.

Synergistic Role of Aerobic Training and Resveratrol on AMPK/PGC1-α/SIRT1 Pathway in the Hippocampus of Rats with Alzheimer's Disease

Background: Alzheimer's disease symptoms indicate that increased Aβ leads to central nervous system dysfunction. Exercise reduces Aβ deposition through the AMPK signaling pathway. Additionally, resveratrol (RSV) has neuroprotective effects related to cognitive decline. Objectives: This study investigated the effects of aerobic training and RSV on the AMPK/PGC-1α/SIRT1 pathway in the hippocampus of Alzheimer's rats. Methods: Thirty-five male Wistar rats were divided into five groups: Normal (NO), Alzheimer's (AD), Alzheimer's-training (ADT), Alzheimer's-resveratrol (ADRSV), and Alzheimer's-training-resveratrol (ADTRSV). The supplement groups received 20 mg of RSV (per kg of body weight) orally during the intervention period. The aerobic exercise program, which included running on a treadmill at speeds of 6 - 18 meters per minute, was performed 5 days a week for eight weeks. Results: Alzheimer's induction caused a significant decrease in the expression of AMPK/PGC-1α/SIRT1 (P = 0.0001). Exercise and RSV significantly increased the expression of AMPK/PGC-1α/SIRT1 in AD rats (P < 0.05). Additionally, significant increases in the expression of AMPK, PGC-1α, and SIRT1 were observed in the ADTRSV group compared to the ADT group (P = 0.034, P = 0.020, and P = 0.038, respectively) and ADRSV (P = 0.026, P = 0.021, and P = 0.021). Conclusions: AD induction was associated with decreased AMPK/PGC-1α/SIRT1 expression. Aerobic exercise and RSV consumption can reverse this decrease. Given the crucial role of this signaling pathway in hippocampal function, alterations in these indicators following physical activity and RSV use may partially mitigate Alzheimer's disease complications.

Abstract P132: Sex Differences in Cerebrovascular Dysfunction in the APP/PS1 TgF344-AD Rat Model of Alzheimer's Disease

Alzheimer's Disease (AD) is the primary cause of dementia and is characterized by extracellular beta-amyloid plaques and intracellular hyperphosphorylated tau-containing neurofibrillary tangles in the brain. Emerging evidence suggests that cerebrovascular dysfunction is associated with AD. Although two-thirds of AD patients are female, sex differences in transgenic AD models have been largely ignored. The present study investigated sex differences in cerebrovascular dysfunction and potential mechanisms in AD using a TgF344-AD rat model. The APP/PS1 TgF344-AD (AD) rats serve as a preferred model to study AD since they recapitulate the complete repertoire of AD-like pathologies in humans. We previously longitudinally characterized cerebral hemodynamics in male TgF344 AD rats at 3, 4, 6, and 14 months, and reported that 4-month-old AD males displayed early signs of impaired cerebral blood flow (CBF) autoregulation and reduced functional hyperemia, two months earlier than memory loss, which was co-occurred with the appearance of plaques. These deficits progressed with advancing age. The present study used 13-14 months of female TgF344-AD (AD) and F344 (WT) rats. We found that AD females also displayed impaired learning and memory function in the eight-arm swim and open field tests as seen in males. Amyloid plaques were prominent in the hippocampus and cortex of female AD brains at a similar level in males, while no plaques were observed in WT brains. Functional hyperemic responses to whisker stimulation were markedly impaired in female AD rats. Further, we found evidence of astrocyte activation and microgliosis in female AD brains using immunohistochemistry and western blots. The astrocytes and microglial activation formed clusters around amyloid plaques. The direct contact between astrocytic endfeet and penetrating arterioles was markedly reduced in AD animals. Moreover, the blood-brain barrier (BBB) was disrupted in AD animals as the tight junction marker ZO1 was significantly reduced in AD brains. These results demonstrate cerebrovascular dysfunction contributes to loss of cognitive function in both male and female APP/PS1 TgF344-AD rats and is associated with impaired functional hyperemia, loss of astrocytic endfeet on penetrating arterioles, BBB breakdown, neuroinflammation related to amyloid plaques. They also indicate that the female TgF344-AD rat is appropriate for studying age-related influences of sex hormones on AD.

Impaired Dynamics of Positional and Contextual Neural Coding in an Alzheimer's Disease Rat Model.

The hippocampal representation of space, formed by the collective activity of populations of place cells, is considered as a substrate of spatial memory. Alzheimer's disease (AD), a widespread severe neurodegenerative condition of multifactorial origin, typically exhibits spatial memory deficits among its early clinical signs before more severe cognitive impacts develop. To investigate mechanisms of spatial memory impairment in a double transgenic rat model of AD. In this study, we utilized 9-12-month-old double-transgenic TgF344-AD rats and age-matched controls to analyze the spatial coding properties of CA1 place cells. We characterized the spatial memory representation, assessed cells' spatial information content and direction-specific activity, and compared their population coding in familiar and novel conditions. Our findings revealed that TgF344-AD animals exhibited lower precision in coding, as evidenced by reduced spatial information and larger receptive zones. This impairment was evident in maps representing novel environments. While controls instantly encoded directional context during their initial exposure to a novel environment, transgenics struggled to incorporate this information into the newly developed hippocampal spatial representation. This resulted in impairment in orthogonalization of stored activity patterns, an important feature directly related to episodic memory encoding capacity. Overall, the results shed light on the nature of impairment at both the single-cell and population levels in the transgenic AD model. In addition to the observed spatial coding inaccuracy, the findings reveal a significantly impaired ability to adaptively modify and refine newly stored hippocampal memory patterns.

Protective effects of L-carnitine against beta-amyloid-induced memory impairment and anxiety-like behavior in a rat model of Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia, leads to neurodegeneration and cognitive decline. We investigated the therapeutic effects of L-carnitine on cognitive performance and anxiety-like behavior in a rat model of AD induced by unilateral intracerebroventricular injection of β-amyloid1-42 (Aβ1-42). L-carnitine (100 mg/kg/day) was administered intraperitoneally for 28 consecutive days. Following this, the open-field test, novel object recognition test, elevated plus-maze test, Barnes maze test, and passive avoidance learning test were used to assess locomotor activity, recognition memory, anxiety-like behavior, spatial memory, and passive avoidance memory, respectively. Plasma and hippocampal oxidative stress markers, including total oxidant status (TOS) and total antioxidant capacity (TAC), were examined. In addition, histological investigations were performed in the dentate gyrus of the hippocampus using Congo red staining and hematoxylin and eosin staining. The injection of Aβ1-42 resulted in cognitive deficits and increased anxiety-like behavior. These changes were associated with an imbalance of oxidants and antioxidants in plasma and the hippocampus. Also, neuronal death and Aβ plaque accumulation were increased in the hippocampal dentate gyrus region. However, injection of L-carnitine improved recognition memory, spatial memory, and passive avoidance memory in AD rats. These findings provide evidence that L-carnitine may alleviate anxiety-like behavior and cognitive deficits induced by Aβ1-42 through modulating oxidative-antioxidant status and preventing Aβ plaque accumulation and neuronal death.

Ginkgo biloba extract inhibits hippocampal neuronal injury caused by mitochondrial oxidative stress in a rat model of Alzheimer's disease.

Ginkgo biloba extracts (GBE) have been shown to effectively improve cognitive function in patients with Alzheimer's disease (AD). One potential therapeutic strategy for AD is to prevent loss of adult hippocampal neurons. While recent studies have reported that GBE protects against oxidative stress in neurons, the underlying mechanisms remain unclear. In this study, an AD-like rat model was established via bidirectional injection of amyloid beta 25-35 (Aβ25-35; 20 μg) in the hippocampal CA1 region. Learning and memory abilities of experimental rats were AD assessed in response to oral administration of 7.5 g/L or 15 g/L Ginkgo biloba extract 50 (GBE50) solution and the peroxidation phenomenon of hippocampal mitochondria determined via analysis of mitochondrial H2O2 and several related enzymes. Levels of the oxidative stress-related signaling factor cytochrome C (Cyto C), apoptosis-related proteins (Bax, Bcl-2 and caspase-3) and caspase-activated DNase (CAD) were further detected via western blot. 8-Hydroxydeoxyguanosine (8-OHdG), the major product of DNA oxidative stress, was evaluated to analyze DNA status. Our results showed elevated H2O2 levels and monoamine oxidase (MAO) activity, and conversely, a decrease in the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the hippocampus of AD rats. Administration of GBE50 regulated the activities of these three enzymes and induced a decrease in H2O2. GBE50 exerted regulatory effects on abnormally expressed apoptotic proteins in the AD rat hippocampus, enhancing the expression of Bcl-2, inhibiting release of Cyto C from mitochondria, and suppressing the level of caspase-3 (excluding cleaved caspase-3). Furthermore, GBE50 inhibited DNA damage by lowering the generation of 8-OHdG rather than influencing expression of CAD. The collective findings support a protective role of GBE50 in hippocampal neurons of AD-like animals against mitochondrial oxidative stress.

Diosmin ameliorates inflammation, apoptosis and activates PI3K/AKT pathway in Alzheimer's disease rats.

Alzheimer's disease (AD), a prevalent cognitive disorder among the elderly, is frequently linked to the abnormal accumulation of myloid-β (Aβ), which is mainly as a result of neuronal death and inflammation. Diosmin, a flavonoid, is considered a potential drug for the treatment of AD. Our study aimed to uncover the molecular mechanism of diosmin in AD therapy. Here, rats were randomly divided into three groups: control, Aβ25-35, and Aβ25-35 + diosmin groups. AD model rats were induced by Aβ25-35 intraventricular injection, meanwhile 50mg/kg diosmin was orally administered for 6-week intervention. Morris water maze test assessed learning and memory abilities. Hippocampal neuronal damage was determined by HE, Nissl, and TUNEL staining. These assays indicate that diosmin improves cognitive dysfunction and reduces hippocampal neuronal loss and apoptosis. Western blot showed that diosmin reduced Bax (1.21 ± 0.12) and cleaved caspase-3 (1.27 ± 0.12) expression, and increased Bcl-2 (0.70 ± 0.06), p-PI3K (0.71 ± 0.08), and p-AKT (0.96 ± 0.10) in the hippocampus. ELISA indicated diosmin reduces IL-1β, IL-6, and TNF-α levels, suggesting anti-inflammation effect. These results suggest that diosmin inhibits neuronal apoptosis and neuroinflammatory responses to improve cognitive dysfunction in AD rats, possibly related to upregulation of the PI3K/AKT pathway, providing a scientific basis for its use in AD treatment.

Unveiling the Therapeutic Potential of Kelulut (Stingless Bee) Honey in Alzheimer's Disease: Findings from a Rat Model Study.

Alzheimer's disease (AD) poses a major worldwide health challenge because of its profound impact on cognitive abilities and overall well-being. Despite extensive research and numerous clinical trials, therapeutic options remain limited. Our study aimed to investigate the potential of Kelulut honey (KH) as a novel therapeutic agent for addressing the multifactorial pathology of AD. We tried to evaluate the disease-attenuating and neuroprotective potential of KH in the intrahippocampally induced AD rat model by utilizing histochemistry and enzyme-linked immunosorbent assay (ELISA) studies. A total of 26 male Sprague Dawley rats weighing ~280-380 g were randomly divided into three groups: Control, AD-induced (Aβ), and AD-induced and treated with KH (Aβ+KH). The latter two groups underwent stereotaxic surgery, where 6.25 µg of amyloid β1-42 peptides were injected intrahippocampally. One-week post-surgery, KH was administered to the treatment group at a dose of 1 g/kg body weight for a period of four weeks, after which the rats went through behavior tests. After completion of behavior analysis, the rats were sacrificed, and the brains were processed for histochemistry and ELISA studies. The open field test analysis demonstrated that KH improved the locomotion of Aβ+KH compared to Aβ (p = 0.0013). In comparison, the Morris water maze did not show any nootropic effects on cognition with a paradoxical increase in time spent in the target quadrant by the Aβ group (p = 0.029). Histochemical staining showed markedly increased Congo-red-stained amyloid plaques, which were significantly reduced in dentate gyrus of Aβ+KH compared to Aβ (p < 0.05). Moreover, significantly higher apoptosis was seen in the Aβ group compared to Aβ+KH (p < 0.01) and control groups (p < 0.001). Furthermore, the ELISA studies deduced more phosphorylated tau in the diseased group compared to Aβ+KH (p = 0.038) and controls (p = 0.016). These findings suggest that KH consumption for twenty-eight days has the potential to attenuate the pathological burden of disease while exerting neuroprotective effects in rodent models of AD.

Yigong San improves cognitive decline in a rat model of Alzheimer's disease by regulating intestinal microorganisms

To investigate the effect of Yigong San (YGS) on learning and memory abilities of rats with lipopolysaccharide (LPS)‑induced cognitive decline and explore its possible mechanism in light of intestinal microbiota. Forty SD rats were randomly divided into control group, model group, donepezil (1.3 mg/kg) group, and high-dose (5.25 g/kg) and low-dose (2.63 g/kg) YGS treatment groups. After 24 days of treatment with the corresponding drugs or water by gavage, the rats in the latter 4 groups received an intraperitoneal injection of LPS (0.5 mg/kg) to establish models of Alzheimer's disease (AD). Water maze test and HE staining were used to evaluate the changes in learning and memory abilities and pathomorphology of the hippocampus. The changes in gut microbial species of the rats were analyzed with 16S rRNA sequencing, and the levels of IL-6, TNF-α, and IL-1β in the brain tissue and serum were detected using ELISA. Compared with the AD model group, the YGS-treated rats showed significantly shortened escape latency on day 5 after modeling, reduced neuronal degeneration and necrosis in the hippocampus, lowered pathological score of cell damage, and decreased levels IL-6, TNF-α and IL-1β in the brain tissue and serum. The YGS-treated rats showed also obvious reduction of Alpha diversity indicators (ACE and Chao1) of intestinal microbiota with significantly increased abundance of Prevotellaceae species at the family level and decreased abundance of Desulfovibrionaceae, which were involved in such metabolic signaling pathways as cell community prokaryotes, membrane transport, and energy metabolism. YGS improves learning and memory abilities and hippocampal pathomorphology in AD rat models possibly by regulating the abundance of intestinal microbial species such as Prevotellaceae to affect the metabolic pathways for signal transduction, cofactors, and vitamin metabolism.