Cognitive Impairment In Alzheimer's Disease Mice Research Articles

Effect of Human Milk Oligosaccharides on Learning and Memory in Mice with Alzheimer's Disease.

Alzheimer's disease (AD) is distinguished by cognitive dysfunction and neuroinflammation in the brain. 2'-Fucosyllactose (2'-FL) is a major human milk oligosaccharide (HMO) that is abundantly present in breast milk and has been demonstrated to exhibit immunomodulatory effects. However, the role of 2'-FL and HMO in gut microbiota modulation in relation to AD remains insufficiently investigated. This study aimed to elucidate the preventive effect of the 2'-FL and HMO impact of AD and the relevant mechanism involved. Here, the behavioral results showed that 2'-FL and HMO intervention decreased the expression of Tau phosphorylation and amyloid-β (Aβ), inhibited neuroinflammation, and restored cognitive impairment in AD mice. The metagenomic analysis proved that 2'-FL and HMO intervention restored the dysbiosis of the gut microbiota in AD. Notably, 2'-FL and HMO intervention significantly enhanced the relative abundance of Clostridium and Akkermansia. The metabolomics results showed that 2'-FL and HMO enhanced the oleoyl-l-carnitine metabolism as potential drivers. More importantly, the levels of oleoyl-l-carnitine were positively correlated with the abundances of Clostridium and Akkermansia. These results indicated that 2'-FL and HMO had therapeutic potential to prevent AD-induced cognitive impairment, which is of great significance for the treatment of AD.

Dietary Xylitol Supplement Ameliorated AD-related Neuronal Injury by Regulating Glucose Metabolism Relevant Amino Acids in Mice.

Alzheimer's disease (AD) is one of the most common irreversible degenerative diseases of the central nervous system. Recent studies have found that patients with AD generally experience abnormal glucose metabolism. Xylitol is a functional sugar alcohol, which has been reported to regulate glucose metabolism. The present study was designed to determine whether xylitol can alleviate cognitive impairment in AD mice. In the current research, 5% xylitol was supplemented in the diet to treat APP/PS1 transgenic AD mice for 2 months. Cognitive ability was measured by the Morris water maze, and anxiety-like behaviors were examined by open-field experiment. Hippocampal cellular apoptosis and mitochondria pathway related apoptotic proteins were tested by TUNEL staining and immunoblotting, respectively. By LC-MS, plasma levels of glucose metabolism intermediates and related amino acids were evaluated. Results showed that xylitol could significantly ameliorate anxiety-like activity in AD mice by partially regulating expression levels of mitochondrial pathway-related apoptotic proteins. Xylitolregulated glucose metabolism may play an important role in the process. The current study suggests that xylitol may be a potential candidate for improving neuropsychiatric behavior in AD by regulating the levels of TCA cycle intermediates and related amino acids in glucose metabolism.

A Reactive Oxygen Species-Responsive Targeted Nanoscavenger to Promote Mitophagy for the Treatment of Alzheimer's Disease.

Mitophagy modulators are proposed as potential therapeutic intervention that enhance neuronal health and brain homeostasis in Alzheimer's disease (AD). Nevertheless, the lack of specific mitophagy inducers, low efficacies, and the severe side effects of nonselective autophagy during AD treatment have hindered their application. In this study, the P@NB nanoscavenger is designed with a reactive-oxygen-species-responsive (ROS-responsive) poly(l-lactide-co-glycolide) core and a surface modified with the Beclin1 and angiopoietin-2 peptides. Notably, nicotinamide adenine dinucleotide (NAD+ ) and Beclin1, which act as mitophagy promoters, are quickly released from P@NB in the presence of high ROS levels in lesions to restore mitochondrial homeostasis and induce microglia polarization toward the M2-type, thereby enabling it to phagocytose amyloid-peptide (Aβ). These studies demonstrate that P@NB accelerates Aβ degradation and alleviates excessive inflammatory responses by restoring autophagic flux, which ameliorates cognitive impairment in AD mice. This multitarget strategy induces autophagy/mitophagy through synergy, thereby normalizing mitochondrial dysfunction. Therefore, the developed method provides a promising AD-therapy strategy.

Loureirin C, from Chinese Dragon's Blood (Dracaena cochinchinensis S.C. Chen), is a novel selective estrogen receptor α modulator with anti-Alzheimer's disease effects

As the incidence of Alzheimer's disease (AD) continues to rise in recent years, there are few therapeutic drugs for AD treatment with limited efficacy. AD occurs twice as often in women as that in men, partially due to the low estrogen level in women after menopause. Phytoestrogens (PEs), similar to endogenous estrogens in chemical structure with neuroprotection and fewer side effects, have good development and application prospects in AD-treatment. Loureirin C is an active ingredient isolated from Chinese Dragon's Blood (CDB) with a similar structure to 17β-E2. In our study, we found that loureirin C targeted to ERα and had partial-agonistic activity using molecular docking prediction and dual-luciferase reporter assay. However, it is still unclear whether loureirin C has estrogenic effects in body, and whether exerts anti-AD effect through ERα. In this paper, the ERα selective inhibitor MPP or ERα specific small interfering RNA (siERα) mediated gene silencing technology were used. Besides,E-SCREEN method were used to evaluate the estrogen effects of loureirin C in vivo and in vitro. MTT assay, Western blot, real-time PCR technology and behaver tests was used to investigate the neuroprotective effect, cognitive function and the underlying mechanism. We found that loureirin C possessed estrogenic activity, had neuroprotective effects in AD cells and improved cognitive impairment in AD mice via ERα. Loureirin C may be a potential candidate for AD.

Double-negative T cells mediate M1 polarization of microglial cells via TNF-α-NLRP3 to aggravate neuroinflammation and cognitive impairment in Alzheimer's disease mice.

We mainly study the role and regulatory mechanism of double-negative T cells(DNTs) in Alzheimer's disease(AD). The mice splenic DNTs were separated and amplified by Rosettesep antibody adsorption method and Easysep magnetic activated cell sorting. DNTs were intraperitoneally injected into the APP/PS1-AD mice model, which was found to aggravate cognitive impairment in mice. DNTs secreted tumor necrosis factor α (TNF-α) to promote the activation of NLRP3 and the M1 polarization of microglial cells, and silencing NLRP3 with small interfering RNA (siRNA) suppressed the effect of DNTs. DNTs were later cocultured with mice microglial cell line BV2, then fluorescence staining was conducted to detect NLRP3 expression, and enzyme-linked immunoassay was performed to measure the expression of inflammatory factors. Moreover, the levels of NLRP3, ASC, and TNFR1 proteins were detected by western-blot assay, and the proportion of F4/80 + CD11b + M1 cells was detected by flow cytometry. DNTs promoted the M1 polarization of BV2 cells and the activation of NLRP3 inflammasome. After treatment of BV2 cells with NLRP3 inhibitor, the effect of DNTs was weakened. Later, TNF-α siRNA was transfected into DNTs, and it was found that DNTs with TNF-α silencing had markedly weakened polarization effect on BV2 cells. We discovered that the proportion of DNTs increased in AD patients. DNTs secreted TNF-α to regulate the activation of NLRP3 inflammasome and the M1 polarization of microglial cells, thus promoting the central inflammatory response and aggravating the cognitive impairment in AD mice.

LncRNA BDNF-AS as ceRNA regulates the miR-9-5p/BACE1 pathway affecting neurotoxicity in Alzheimer's disease

IntroductionThe long non-coding RNA Brain-derived nutritional factor anti-sense RNA (BDNF-AS) is a type of anti-sense RNA that has been proven to play a crucial role in the occurrence and development of certain nervous system disorders. However, the role and molecular mechanism of BDNF-AS in Alzheimer's disease (AD) have not been elucidated yet. MethodsPeripheral blood samples were collected from outpatients with AD as well as from normal elderly individuals in the community, and the expression of BDNF-AS was analysed using quantitative reverse transcription-polymerase chain reaction. An in vitro model was constructed, and the effect of BDNF-AS expression level on the cells was measured using the CCK8 method and flow cytometry. The molecular biological mechanism of BDNF-AS in AD was examined using the luciferase reporter, MS2-RIP, and RNA pulldown assays. ResultWe found that the expression of BDNF-AS was elevated in the peripheral blood of patients with AD and that increased BDNF-AS expression may be associated with the cognitive status of such patients. The results confirmed that BDNF-AS could promote neurotoxicity in the in vitro model. Then, we uncovered that BDNF-AS promotes the expression of BACE1 through the competitive binding of miR-9-5p, thereby promoting amyloid deposition. Finally, through the Morris water maze, we found that the high expression of BDNF-AS promoted cognitive impairment in AD mice. ConclusionThe obtained results suggest that BDNF-AS plays a crucial role in the occurrence and development of AD. As a new pathogenic gene of AD, BDNF-AS may be used as a therapeutic target or as a prognostic marker in patients with AD.

Non-genomic rewiring of vitamin D receptor to p53 as a key to Alzheimer's disease.

Observational epidemiological studies have associated vitamin D deficiency with Alzheimer's disease (AD). However, whether vitamin D deficiency would result in some impacts on the vitamin D binding receptor (VDR) remains to be characterized in AD. Vitamin D helps maintain adult brain health genomically through binding with and activating a VDR/retinoid X receptor (RXR) transcriptional complex. Thus, we investigated the role of VDR in AD using postmortem human brains, APP/PS1 mice, and cell cultures. Intriguingly, although vitamin D was decreased in AD patients and mice, hippocampal VDR levels were inversely increased. The abnormally increased levels of VDR were found to be colocalized with Aβ plaques, gliosis and autophagosomes, implicating a non‐genomic activation of VDR in AD pathogenesis. Mechanistic investigation revealed that Aβ upregulated VDR without its canonical ligand vitamin D and switched its heterodimer binding‐partner from RXR to p53. The VDR/p53 complex localized mostly in the cytosol, increased neuronal autophagy and apoptosis. Chemically inhibiting p53 switched VDR back to RXR, reversing amyloidosis and cognitive impairment in AD mice. These results suggest a non‐genomic rewiring of VDR to p53 is key for the progression of AD, and thus VDR/p53 pathway might be targeted to treat people with AD.

Schisandrin Inhibits NLRP1 Inflammasome-Mediated Neuronal Pyroptosis in Mouse Models of Alzheimer's Disease.

BackgroundIn recent years, schisandrin (SCH) was proved to improve Alzheimer's Disease (AD). The aim of our study is to explore the effect of SCH on neuronal pyroptosis in the disease.MethodsA Morris water maze test was performed to evaluate the spatial learning and memory retention of AD mouse. ELISA was fulfilled to examine the concentration of Aβ, IL-1β, and IL-18. Western blot was performed to detect the expression of apoptosis- and pyroptosis-related proteins. Besides, the neuronal apoptosis rate was examined using TUNEL assay. Immunohistochemistry was utilized to detect the activation of NLRP1 inflammasome.ResultsHere, AD mice have serious cognitive impairment. Meantime, Aβ was highly expressed in the brains of AD mice. SCH could effectively rescue the cognitive impairment in AD mice and impede the production of Aβ. Subsequently, we further demonstrated that SCH repressed neuronal apoptosis, pyroptosis-related proteins expression, and the activation of NLRP1 inflammasome in the hippocampus of AD mice. We also proved that Aβ induced neuronal apoptosis and pyroptosis in vitro. However, the effects of Aβ on neuronal apoptosis and pyroptosis were partly reversed by SCH treatment.ConclusionOverall, our data indicated that SCH improved cognitive impairment in AD mice through inhibition of NLRP1 inflammasome-mediated neuronal pyroptosis and neuronal apoptosis. Our works provided new evidence to support SCH acting as a potential treatment method in AD.

Longan (Dimocarpus longan Lour.) Aril ameliorates cognitive impairment in AD mice induced by combination of D-gal/AlCl3 and an irregular diet via RAS/MEK/ERK signaling pathway

Ethnopharmacological relevanceAccording to the theory of traditional Chinese medicine (TCM), Alzheimer's disease (AD) is identified as “forgetfulness” or “dementia”, and it can be caused by spleen deficiency. Longan Aril (the aril of Dimocarpus longan Lour., LA) is a kind of Chinese medicine, and it can improve intelligence attributed to entering the spleen-meridian. This study aimed to explore the therapeutic effects of LA on AD mice with spleen deficiency, and to understand anti-AD mechanism of LA. Material and methodsA mouse model of AD with spleen deficiency was established by D-gal (140 mg/kg, intraperitoneal injection) and AlCl3 (20 mg/kg, intragastrical administration) in combination with an irregular diet for 60 days, in which mice in LA group were daily given LA (0.5, 1.0 or 2.0 g/kg). The anti-AD effects of LA were evaluated by the Morris water maze, enzyme-linked immunosorbent assay (ELISA), hematoxylin and eosin (H&E), Nissl, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays. The anti-AD mechanism of LA was studied by using metabolomics, and the expressions of RAS/MEK/extracellular signal-regulated kinase (ERK) signaling pathway-related proteins were detected by Western blotting. ResultsLA improved learning and memory abilities, superoxide dismutase (SOD) level, and form and number of Nissl bodies, while reduced the levels of Aβ42, phosphorylated-tau (p-tau), reactive oxygen species (ROS), malondialdehyde (MDA), monoamine oxidase-B (MAO-B), histological injury, and apoptosis rate in AD group (P < 0.05, P < 0.01 or P < 0.001). The anti-AD mechanism of LA may be related to RAS/MEK/ERK and other signaling pathways, in which the expressions of RAS/MEK/ERK signaling pathway-related proteins significantly reduced (P < 0.05 or P < 0.01). ConclusionsLA could improve the cognitive ability and reduce the pathologic impairment in AD mice, which might be partly mediated via inhibition of RAS/MEK/ERK singling pathway.

Ganoderma lucidum Triterpenoids (GLTs) Reduce Neuronal Apoptosis via Inhibition of ROCK Signal Pathway in APP/PS1 Transgenic Alzheimer's Disease Mice.

Alzheimer's disease (AD) is the most common cause of dementia among senior citizen. Ganoderma lucidum triterpenoids (GLTs) have nutritional health benefits and has been shown to promote health and longevity, but a protective effect of GLTs on AD damage has not yet been reported. The objective of this research was to elucidate the phylactic effect of GLTs on AD model mice and cells and to explore its underlying mechanisms. Morris water maze (MWM) test was conducted to detect changes in the cognitive function of mice. Hematoxylin-eosin (HE) staining was applied to observe pathological changes in the hippocampus. Silver nitrate staining was applied to observe the hippocampal neuronal tangles (NFTs). Apoptosis of the hippocampal neurons in mouse brain tissue was determined by TUNEL staining. The expression levels of apoptosis-related protein Bcl2, Bax, and caspase 3/cleaved caspase 3; antioxidative protein Nrf2, NQO1, and HO1; and ROCK signaling pathway-associated proteins ROCK2 and ROCK1 were measured by western blot. In vivo experiments show that 5-month-old APP/PS1 mice appeared to have impaired acquisition of spatial learning and GLTs could reduce cognitive impairment in AD mice. Compared to normal mice, the hippocampus of APP/PS1 mouse's brains was severely damaged, while GLTs could alleviate this symptom by inhibiting apoptosis, relieving oxidative damage, and inactivating the ROCK signaling pathway. In in vitro cell experiments, Aβ25-35 was applied to induce hippocampal neurons into AD model cells. GLTs promoted cell proliferation, facilitated superoxide dismutase (SOD) expression, and inhibited malondialdehyde (MDA) and lactic dehydrogenase (LDH) expression of neurons. Our study highlights that GLTs improve cognitive impairment, alleviate neuronal damage, and inhibit apoptosis in the hippocampus tissues and cells in AD through inhibiting the ROCK signaling pathway.

Sustained release of bioactive hydrogen by Pd hydride nanoparticles overcomes Alzheimer's disease

Oxidative stress-induced mitochondrial dysfunction plays an important role in the pathogenesis of Alzheimer's disease (AD). Hydrogen molecule, a special antioxidant, can selectively scavenge highly cytotoxic reactive oxygen species such as ·OH, exhibiting a potential to treat AD by reducing oxidative stress. However, there is no effective route to realize the continuous and efficient accumulation of administrated hydrogen in AD brain owing to its low solubility. Here, we develop the small-sized Pd hydride (PdH) nanoparticles for high payload of hydrogen and in situ sustained hydrogen release in AD brain. By virtue of the catalytic hydrogenation effect of Pd, the released hydrogen from PdH nanoparticles exhibits high bio-reductivity in favor of effectively scavenging cytotoxic ·OH in a self-catalysis way. Bio-reductive hydrogen is able to recover mitochondrial dysfunction, inhibit Aβ generation and aggregation, block synaptic and neuronal apoptosis and promote neuronal energy metabolism by eliminating oxidative stress and activating the anti-oxidative pathway, consequently ameliorating the cognitive impairment in AD mice. The proposed hydrogen-releasing nanomedicine strategy would open a new window for the treatment of AD.

In vivo and in vitro studies on the roles of p38 mitogen-activated protein kinase and NADPH-cytochrome P450 reductase in Alzheimer's disease.

Alzheimer's disease (AD) is a chronic neurodegenerative disease with an increasing morbidity rate. As one of the most important signaling pathways that responds to inflammation and degeneration, the p38 mitogen-activated protein kinase (MAPK) signaling pathway is active in the cortexes of AD mice. At the cellular level the same effect can be observed with p38 MAPK when induced by amyloid β (Aβ)1–42, a 42-residue Aβ fragment. Inhibition of p38 MAPK in the present study protected SH-SY5Y cells from the toxicity of Aβ1–42, and alleviated the formation of senile plaques and cognitive impairment in AD mice. The expression of cytochrome P450 reductase (CPR) in the brains of mice with AD, in addition to Aβ1–42-treated SH-SY5Y cells, also increased. However, the inhibition of CPR did not protect SH-SY5Y cells from the toxicity of Aβ1–42. The results of the present study suggest that p38 MAPK is a potential therapeutic target for the treatment of AD. In addition, the main enzyme that metabolizes drugs, CPR, could serve a more complex role in AD.

Chronic kidney disease accelerates cognitive impairment in a mouse model of Alzheimer's disease, through angiotensin II

Epidemiological studies suggest that chronic kidney disease (CKD) is a significant risk factor in the development of cognitive decline. However, the exact role of CKD in cognitive impairment or dementia is unclear. This work was performed to examine the potential impact of CKD on cognitive impairment in Alzheimer's disease (AD), focusing on angiotensin II. (1) CKD was induced in 5XFAD mice, an AD model mouse, and wild-type mice by feeding an adenine-containing diet and the effect on cognitive function was compared between both strains. There was no significant difference regarding the severity of CKD induced by adenine between the strains. In 5XFAD mice, the CKD group exhibited significant cognitive impairment while the control group (control diet-fed group) did not, as evidenced by a passive avoidance test. On the other hand, in wild-type mice, neither the CKD group nor the control group showed cognitive impairment. Thus, CKD itself appears to accelerate cognitive impairment in AD mice. (2) We also examined the effect of olmesartan, an angiotensin II receptor blocker, on 5XFAD mice with CKD to elucidate the potential involvement of angiotensin II. As evidenced by the findings of the water maze test, olmesartan treatment significantly ameliorated the impairment of spatial learning and memory function induced by CKD in 5XFAD mice. Olmesartan treatment significantly ameliorated blood-brain barrier (BBB) disruption induced by CKD in 5XFAD mice. Furthermore, olmesartan reduced hippocampal oxidative stress in 5XFAD with CKD to similar levels to the control group of 5XFAD fed standard diet. Hence, the amelioration of CKD-induced cognitive impairment in 5XFAD mice by olmesartan appears to be mediated by the suppression of BBB disruption or oxidative stress. In conclusion, we obtained the evidence suggesting that CKD itself accelerates cognitive impairment in AD mice, through angiotensin II. Thus, our work provides a novel insight into the underlying mechanism of the link between CKD and AD.

SAK3, AN T-TYPE CA2+ CHANNEL STIMULATOR INHIBITS AMYLOID BETA ACCUMULATION

We recently developed a novel cognitive enhancer of an Alzheimer disease (AD) therapeutic candidate ST101 (Phase II in USA) which stimulates T-type voltage-gated Ca2+ channels (T-VGCC) (Moriguchi et al., J Neurochem 2012;121:44-53). In Phase II trial, ST101 by combination is donepezil is significantly improved cognition in AD patients. We here introduced another spiroimidazopyridine derivatives (SAK compounds) (PCT/JP2013/051388), which are much stronger than ST101 when assessed by Ca2+ conductance of T-VGCC with neuronal cells transfected Cav3.1 gene. We evaluated its cognitive improvement and its inhibition of amyloid beta (1-42) accumulation in AD model (APP23) mice. SAK3 treatment significantly enhanced mouse hippocampal LTP. Likewise, SAK3 administration in vivo enhanced the hippocampal glutamate release in mouse hippocampus. The SAK3-induced glutamate release was inhibited by treatment with T-VGCC inhibitor. Consistent with these observations, SAK3 improved cognition in novel objective recognition task in APP23 mice. We also confirmed that the cognitive impairment in AD model mice is improved by 2-3 month treatment with SAK3 (05.mg/kg). The prolonged administration of SAK3 also suppressed the amyloid beta (1-42) accumulation in AD model mice. Taken together, the novel T-VGCC stimulator SAK3 elicits the enhancement of glutamate release in the hippocampus, thereby likely improving cognitive impairment in AD mice. We are looking for a partner company to conduct the preclinical studies to develop SAK3 as novel AD therapeutics.

Chronic hypoxia facilitates Alzheimer's disease through demethylation of γ-secretase by downregulating DNA methyltransferase 3b

IntroductionEnvironmental factors and epigenetic mechanisms are believed to contribute to Alzheimer's disease (AD). We previously documented that prenatal hypoxia aggravated the cognitive impairment and neuropathology in offspring mice. Here, we investigate the chronic hypoxia-induced epigenetic modifications in AD. MethodsThe 3-month-old APPswe/PS1dE9 mice were exposed to hypoxic environment 6 hour/day for 30 days, followed by learning and memory tests and biochemical and neuropathology measurement at the age of 4, 6, and 9 months. ResultsWe found hypoxia exaggerated the neuropathology and cognitive impairment in AD mice. Chronic hypoxia induced demethylation on genomic DNA and decreased the expression of DNA methyltransferase 3b (DNMT3b) in vivo. We further found that DNMTs inhibition elevated the protein levels of amyloid precursor protein, β- and γ-secretases, whereas overexpression of DNMT3b suppressed the levels of them in vitro. DiscussionOur study suggests chronic hypoxia can aggravate AD progression through demethylation of genes encoding γ-secretase components by downregulation of DNMT3b.

Fibrinogen and β-Amyloid Association Alters Thrombosis and Fibrinolysis: A Possible Contributing Factor to Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder in which vascular pathology plays an important role. Since the beta-amyloid peptide (Abeta) is a critical factor in this disease, we examined its relationship to fibrin clot formation in AD. In vitro and in vivo experiments showed that fibrin clots formed in the presence of Abeta are structurally abnormal and resistant to degradation. Fibrin(ogen) was observed in blood vessels positive for amyloid in mouse and human AD samples, and intravital brain imaging of clot formation and dissolution revealed abnormal thrombosis and fibrinolysis in AD mice. Moreover, depletion of fibrinogen lessened cerebral amyloid angiopathy pathology and reduced cognitive impairment in AD mice. These experiments suggest that one important contribution of Abeta to AD is via its effects on fibrin clots, implicating fibrin(ogen) as a potential critical factor in this disease.