Demethyleneberberine attenuates combined cognitive and metabolic dysfunctions in an insulin-resistance-induced Alzheimer's disease rat model: Synthesis, in-silico and in-vivo insights.

To determine the influence of tanshinone on the levels of nitric oxide synthase (NOS) and acetylcholinesterase (AChE) in the brain of an Alzheimer's Disease (AD) rat model and on its potential therapeutic mechanism. 100 Male Sprague Dawley rats were divided into three groups: control group, model group and tanshinone treatment group. 10 microg A beta 1-42 was injected bilaterally into the dorsal lateral region of the dentate gyrus in the hippocampus of rats in the model and tanshinone treatment groups to prepare the AD models. 24h after modeling, tanshinone, 50mg/kg, was administered by gastric perfusion to rats in the tanshinone treatment group. Later, immunohistochemical assay and Western blot analysis were used to detect expression of neuronal NOS (nNOS) and inducible NOS (iNOS) in the rat hippocampus. Activity of AChE in each subregion (CA1 approximately CA4) of rats' hippocampus was determined by a histochemical technique. Expression of nNOS in the model group was down-regulated whereas iNOS was up-regulated. After A beta 1-42 injection, the number of AChE positive fibers in each subregion (CA1 approximately CA4) of the hippocampus was decreased compared with controls. With tanshinone administration, the changes were improved to varying degrees. Tanshinone modulates AChE and NOS proteins concentrations in the hippocampus of AD rats. This may have therapeutic potential in AD rats.

To discuss the value of 11C-PIB PET and 18F-FDG micro PET imaging in Alzheimer's disease (AD) rat model. The AD rat model was established by injection of Abeta1-40 into rat's hippocampus. Learning and memory function were estimated by the Morris water maze. Amyloid deposit and neuron loss were observed by Congo red staining and HE staining respectively. 11C-PIB PET and 18F-FDG micro PET scan were performed. Meanwhile the findings of PET imaging were compared with the results of behavior test and histology. The uptake of 18F-FDG in hippocampus of AD rat model group was lower than that of control group (P < 0.01). The Morris water maze showed that the escape latent period of rat model group was longer than that of control group (P < 0.01). Neuron loss was found in rat model brain. Thus the result of micro-PET imaging was matched with those of the Morris water maze and HE staining. 11C-PIB was specifically bound to beta-amyloid in rat model brain, the uptake of 11C-PIB in AD rat model was higher than that of control (P < 0.05). Abeta deposit was observed in Congo red staining so that the result of 11C-PIB Micro-PET imaging was matched with that of beta-amyloid deposition. 11C-PIB Micro-PET imaging shows the plaque deposition while 18F-FDG PET imaging reflects the change of glucose metabolism in hippocampus in AD rat model. And PET scan can be used to verify the successful establishment of AD model rat model.

Baicalin has been shown to promote spatial learning and neural regeneration, which might increase the differentiation of neural stem cells in Alzheimer's disease (AD) rat models. We aimed to study the role of baicalin on neuronal pentraxin-1 (NPTX-1), neuronal pentraxin-2 (NPTX-2), and C-reactive protein (CRP) in AD model rats. The 30 male Sprague Dawley rats were divided into three groups: the control group, the AD model group, and the AD + baicalin group. Then, the Morris water maze was used to verify the effect of baicalin on the memory and spatial learning of rats. Immunohistochemistry and immunofluorescence were used to observe the expression of NPTX-1, NPTX-2, and CRP in brain tissue. Compared with the AD model group, the AD rats treated with baicalin spent significantly less time finding escape latencies (P = 0.008) and had longer cross-platform times in the target quadrant (P = 0.015). In addition, the AD + baicalin group had significantly higher numbers of hippocampal neurons compared with the AD model group (P < 0.05). Baicalin also obviously decreased the apoptosis of neurons. Moreover, compared with the AD model group, the NPTX-1 and CRP expression in the AD + baicalin group was significantly reduced (P = 0.000) while the expression of NPTX-2 in the brain tissue of AD rats was significantly increased (P = 0.000). Baicalin can play a therapeutic role by downregulating NPTX-1, upregulating NPTX-2, and downregulating CPR in AD model rats.

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

Schisandra chinensis (Turcz.) Baill is produced mainly in northeast China, Korea and Japan. Its fruit has been used in food as a nutritional and functional ingredient for centuries. Polysaccharide is an important chemical component in Schisandra. Previous studies have shown that Schisandra polysaccharide (SCP) could be used to improve cognitive function clinically and treat age-related neurodegenerative disorders. In this study, a urinary metabolomics method based on ultra-high-performance liquid chromatography combined with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) was established to investigate the change of endogenous metabolites in an amyloid β-protein (Aβ) 25-35-induced Alzheimer's disease (AD) rat model. Meanwhile, levels of 9 neurotransmitters were evaluated with ultrahigh-performance liquid chromatography-triple-quadrupole mass spectrometry (UHPLC-TQ-MS) to explore the therapeutic mechanisms of SCP on the AD rat model. Additionally, the synthesis of phosphorylated tau protein (p-tau), acetylcholinesterase (AchE) activity and oxidative damage in the brain of the AD rats were assessed using glycogen synthase kinase-3β (GSK3β), AchE and antioxidant assays, NOS (nitric oxide synthase) and SOD (superoxide dismutase), respectively. The results indicated that the AD model was established successfully and the inducement of Aβ25-35 caused the phosphorylation of tau protein and the deposition of Aβ. In the AD model rats, the levels of AchE, GSK-3β and NOS were significantly elevated and SOD activity was reduced. In the hippocampus of the model rats, the contents of γ-aminobutyric acid, acetylcholine, glycine, norepinephrine, taurine, serotonin and dopamine were significantly decreased and the contents of glutamate and aspartic acid were increased significantly. However, SCP could reduce the degree of phosphorylation of tau protein, the deposition of Aβ and oxidative damage and reverse these changes of neurotransmitters in the AD rats. In a metabolomics study, a total of 38 metabolites were finally identified as potential biomarkers of AD and all of them had a significant recovery compared with the AD model after SCP administration. Metabolomics studies have shown that SCP plays a role in protecting the central nervous system, regulating intestinal microbial metabolism, regulating energy metabolism, and promoting antioxidant effects by regulating the levels of endogenous metabolites in related pathways. This is first report of the use of urine metabolomics combined with the evaluation of 9 neurotransmitter levels to investigate the mechanism of SCP on the treatment of AD.

The study of therapeutic efficacy and mechanisms of Schisandra chinensis and Evodia rutaecarpa combined treatment in a rat model of Alzheimer's disease

To explore the effects of proBDNF on cell proliferation and differentiation in hippocampal dentate gyrus in Alzheimer' disease (AD) rat model. The AD rat model was established. Alzet osmotic minipumps were connected to right hippocampus of AD rat and filled with proBDNF, sheep antibody to proBDNF or normal sheep serum respectively. Rats received the injection for 14 days at the speed of 0.5 microl/h. 5-bromo-2'-deoxyuridine (BrdU, 50 mg/kg, ip) was injected twice daily for 14 days. BrdU immunohistochemistry was processed to determine the number of newly generated cells. To examine the phenotype of newly generated cells, immunofluorescent triple labeling was conducted to colocalize BrdU-positive cells with rabbit anti-doublecortin (DCX) or mouse anti-glial fibrillary acid protein (GFAP). proBDNF group had fewer BrdU positive cells in dentate gyrus (P < 0.01), while anti-proBDNF group had more BrdU positive cells (P < 0.01) as compared with control group respectively. Immunofluorescent triple labeling showed that there was no phenotypic difference of BrdU positive cells between each group. proBDNF can suppress the proliferation of hippocampal neuron in dentate gyrus in AD rats while anti-proBDNF has the opposite effect. These findings suggest that promoting the hippocampal neurogenesis by blocking the functions of endogenous proBDNF may be a potential therapeutic strategy for AD.

Poria cocos polysaccharide (PCP) is a compound from Poria cocos, and which is used as a classical tonic agent. This article aims to investigate the effects of PCP on neuronal damage of hippocampus and cognitive function in a rat model of Alzheimer's disease induced by D-galactose and aluminum trichloride. Oxiracetam (ORC) was used as a positive drug in this experiment. The rats were treated with PCP at doses of 100, 200 and 300 mg/kg/day for 30 days and ORC at dose of 346 mg/kg/day after modeling. The results of behavioral test showed that PCP could prevent cognitive decline in Alzheimer's disease rats as assessed by Y-maze test and Morris water maze test. Results of hippocampus slices showed that neurons were integrated and regularly arranged in the groups, which were administered along with PCP. Moreover, PCP could reduce neuronal apoptosis in hippocampus of Alzheimer's disease rats. Furthermore, the activities of superoxide dismutase in the hippocampus were elevated by PCP administration, while acetyl cholinesterase, reactive oxygen, malondialdehyde and inflammatory factors levels were reduced. In addition, we found PCP could attenuate MAPK/NF-κB signal pathway in the hippocampus. All results illustrated that PCP could exert neuroprotective effects at least partly through alleviating oxidative stress, apoptosis, inflammation and inhibiting the MAPK/NF-κB pathway in Alzheimer's disease rats induced by D-galactose and aluminum trichloride.

Objective To investigate the effects of tenuigenin (TEN) on expression of brain-derived neurotrophic factor (BDNF), and its receptor tyrosine protein kinase B (TrkB) in the hippocampal CA1 region of Alzheimer's disease (AD) model rats. Methods Sixty male Wistar rats were divided randomly into 4 groups: the control group, the model group, 12.50 mg/ml TEN group and 37.50 mg/ml TEN group. AD model rats were made by injecting ibotenic acid into Meynert basal nuclei of aging rats induced by D-galactose. The expressions of BDNF and its receptor TrkB in the hippocampal CA1 region were measured by immunohistochemistry method. Results The positive expressions of BDNF and TrkB were pale brown and mainly in neuronal cell membrane of the hippocampal CA1 region measured by immunohistochemistry method. The average absorbance values of BDNF and its receptor TrkB in the control group were 0.47 ± 0.02 and 0.46 ± 0.05, while in the model group were 0.30 ± 0.02 and 0.21 ± 0.07 which were significantly lower than that of the control group (P = 0.000, for all). The average absorbance values of BDNF and its receptor TrkB in 12.50 mg/ml TEN group were 0.35 ± 0.05 and 0.32 ± 0.07, which were significantly higher than that of the model group ( P = 0.000, for all) and 37.50 mg/ml TEN group were 0.43 ± 0.05 and 0.37 ± 0.03, which were significantly higher than that of the model group ( P = 0.000, for all). The average absorbance values of BDNF and its receptor TrkB in 37.50 mg/ml TEN group increased significantly than that in 12.50 mg/ml TEN group ( P = 0.000). Conclusions TEN can dose-dependently increase BDNF and its receptor TrkB expression in the hippocampal CA1 region of Alzheimer's disease model rats, which may partly explain the beneficial effects of TEN on cognitive function. doi: 10.3969/j.issn.1672-6731.2014.05.011

The aim of this study was to investigate the therapeutic effects and related mechanisms of Tanshinone IIA and Tetramethylpyrazine O/W composite nanoemulsions on Alzheimer's disease (AD) rats. The therapeutic effect of TSN/TMP O/W NEs on AD rats was evaluated by behavioral tests, H&E, Nissl, and Immunohistochemistry staining. ELISA and Western blot were used to analyze the mechanism. The results showed that TSN/TMP O/W NEs could down-regulate the expression of Bax and Caspase-3 proteins, decrease the level of MDA, increase the expression of SOD and GSH-Px, and alleviate cognitive impairment in AD rats. TSN/TMP O/W NEs can inhibit MAPK/ERK/CREB signaling pathway and effectively alleviate cognitive impairment, oxidative stress injury, and neuronal apoptosis in AD rats.

Cognitive dysfunction in Alzheimer's disease is strongly associated with a reduction in synaptic plasticity, which may be induced by oxidative stress. Testosterone is beneficial in learning and memory, although the underlying protective mechanism of testosterone on cognitive performance remains unclear. This study explored the protective mechanism of a subcutaneous injection of 0.75 mg testosterone on cognitive dysfunction induced by bilateral injections of amyloid beta 1-42 oligomers into the lateral ventricles of male rats. Morris water maze test results demonstrated that testosterone treatment remarkably reduced escape latency and path length in Alzheimer's disease rat models. During probe trials, testosterone administration significantly elevated the percentage of time spent in the target quadrant and the number of platform crossings. However, flutamide, an androgen receptor antagonist, inhibited the protective effect of testosterone on cognitive performance in Alzheimer's disease rat models. Nissl staining, immunohistochemistry, western blot assay, and enzyme-linked immunosorbent assay results showed that the number of intact hippocampal pyramidal cells, the dendritic spine density in the hippocampal CA1 region, the immune response and expression level of postsynaptic density protein 95 in the hippocampus, and the activities of superoxide dismutase and glutathione peroxidase were increased with testosterone treatment. In contrast, testosterone treatment reduced malondialdehyde levels. Flutamide inhibited the effects of testosterone on all of these indicators. Our data showed that the protective effect of testosterone on cognitive dysfunction in Alzheimer's disease is mediated via androgen receptors to scavenge free radicals, thereby enhancing synaptic plasticity.

Both oxidative stress and inflammation are elevated in brains of Alzheimer's disease patients, but their pathogenic significance still remains unclear. Current evidence support the hypothesis that non-steroidal anti-inflammatory drugs (NSAIDs) and antioxidant therapy might protect against the development of Alzheimer's disease, and ibuprofen has the strongest epidemiological support. In the present work our attention was focused on (R)-alpha-lipoic acid considered as a potential neuroprotective agent in Alzheimer's disease therapy. In particular, we investigated a new co-drug (1) obtained by joining (R)-alpha-lipoic acid and ibuprofen via a diamide bond, for evaluating its potential to antagonize the deleterious structural and cognitive effects of beta-amyloid (1-40) in an infused Alzheimer's disease rat model. Our results indicated that infusion of beta-amyloid (1-40) impairs memory performance through a progressive cognitive deterioration; however, ibuprofen and co-drug 1 seemed to protect against behavioural detriment induced by simultaneous administration of beta-amyloid (1-40) protein. The obtained data were supported by the histochemical findings of the present study: beta-amyloid protein was less expressed in 1-treated than in ibuprofen and (R)-alpha-lipoic acid alone-treated cerebral cortex. Taken together, the present findings suggest that co-drug 1 treatment may protect against the cognitive dysfunction induced by intracerebroventricular infusion of beta-amyloid (1-40) in rats. Thus, co-drug 1 could prove useful as a tool for controlling Alzheimer's disease-induced cerebral amyloid deposits and behavioural deterioration.

To study the pharmacokinetics of active ingredients (alkaloids, iridoids and flavonoids) in Huanglian Jiedu decoction (HLJDD) in Alzheimer's disease (AD) model rats, and investigate its mechanism in treatment of AD. All of rats were divided into normal control group (n=6), shame operation group (n=6) and model group (n=12). Rats in shame operation group received daily subcutaneous injection of D-galactose (D-gal 50 mg·kg⁻¹) for a total of 45 d to induce subacute aging model. Based on the operation of shame operation group, the rats in model group were given with an injection of Aβ₂₅₋₃₅ (4.0 g·L⁻¹)-ibotenic acid (2.0 g·L⁻¹) into the nucleus basalis magnocellularis. Then rats in model group were divided into HLJDD one day administration group (n=6) and HLJDD one week group (n=6). The plasma concentration of alkaloids, iridoid and flavonoids was determined by liquid chromatography tandem mass spectrometry (LC-QQQ-MS) at different time points. The levels of seven inflammatory factors (MIP-2, IL-1β, IL-2, IL-8, IL-10, IL-13, TNF-α) in cerebrospinalfluid (CSF) were measured by Bio-Plex multi-factor detection technology. Iridoids in AD model rats, with high bioavailability, were easily absorbed and eliminated. The plasma concentration of alkaloid was lower, and the AUC (area under the curve) was higher in HLJDD one week group than that in HLJDD one day group. The plasma concentration-time curves of flavonoids showed obvious bimodal phenomena. After the gastric administration of HLJDD, the inflammatory factors in CSF of AD rats demonstrated a callback trend, including IL-1β/IL-10 (P<0.05) with significant difference. The pharmacokinetic behaviors of iridoids, alkaloids and flavonoids (41 compounds) in AD model rats were fundamentally elucidated, and HLJDD can improve the central inflammatory status of AD rats by regulating the levels of inflammatory factors.

Currently, Alzheimer’s disease (AD) cannot be treated effectively. Mesenchymal stem cells (MSCs)-derived extracellular vesicles (EVs) (MSC-EVs) exhibit therapeutic effects on many diseases. This study investigated the mechanism of bone marrow MSC-EVs (BM-MSC-EVs) in a rat model of AD. The cognitive function, amyloid-β (Aβ) plaques, Aβ deposition areas and levels of Aβ1-42, Aβ decomposition-related factors (NEP and IDE), and inflammatory cytokines in BM-MSC-EVs-treated AD rats were measured. The effect of BM-MSC-EVs was studied in AD neuron model. microRNA (miR)-29c-3p and BACE1 expression, as well as levels of Wnt/β-catenin pathway-related factors in AD and EVs-treated AD models were detected. miR-29c-3p relationship with BACE1 was predicted and confirmed. miR-29c-3p and BACE1 were interfered to verify the mechanism of EVs in AD. The Wnt/β-catenin pathway inhibitor DKK1 was further added to EVs-treated AD neurons. BM-MSC-EVs showed therapeutic effects on AD rats and neurons. BM-MSC-EVs carried miR-29c-3p into AD neurons. miR-29c-3p targeted BACE1. Silencing miR-29c-3p in BM-MSCs reduced BM-MSC-EV therapeutic effect on AD, which was reversed after BACE1 knockdown. miR-29c-3p targeted BACE1 and activated the Wnt/β-catenin pathway, and the Wnt/β-catenin pathway inhibition impaired EV therapeutic effects on AD. We highlighted that BM-MSC-EVs delivered miR-29c-3p to neurons to inhibit BACE1 expression and activate the Wnt/β-catenin pathway, thereby playing a therapeutic role in AD. This study may provide a novel perspective for elucidating the mechanism of MSCs in the treatment of AD.

Naringenin improves learning and memory in an Alzheimer's disease rat model: Insights into the underlying mechanisms