Brains Of SAMP8 Mice Research Articles

Panax notoginseng saponins prevent dementia and oxidative stress in brains of SAMP8 mice by enhancing mitophagy

BackgroundMitochondrial dysfunction is one of the distinctive features of neurons in patients with Alzheimer’s disease (AD). Intraneuronal autophagosomes selectively phagocytose and degrade the damaged mitochondria, mitigating neuronal damage in AD. Panax notoginseng saponins (PNS) can effectively reduce oxidative stress and mitochondrial damage in the brain of animals with AD, but their exact mechanism of action is unknown.MethodsSenescence-accelerated mouse prone 8 (SAMP8) mice with age-related AD were treated with PNS for 8 weeks. The effects of PNS on learning and memory abilities, cerebral oxidative stress status, and hippocampus ultrastructure of mice were observed. Moreover, changes of the PTEN-induced putative kinase 1 (PINK1)-Parkin, which regulates ubiquitin-dependent mitophagy, and the recruit of downstream autophagy receptors were investigated.ResultsPNS attenuated cognitive dysfunction in SAMP8 mice in the Morris water maze test. PNS also enhanced glutathione peroxidase and superoxide dismutase activities, and increased glutathione levels by 25.92% and 45.55% while inhibiting 8-hydroxydeoxyguanosine by 27.74% and the malondialdehyde production by 34.02% in the brains of SAMP8 mice. Our observation revealed the promotion of mitophagy, which was accompanied by an increase in microtubule-associated protein 1 light chain 3 (LC3) mRNA and 70.00% increase of LC3-II/I protein ratio in the brain tissues of PNS-treated mice. PNS treatment increased Parkin mRNA and protein expression by 62.80% and 43.80%, while increasing the mRNA transcription and protein expression of mitophagic receptors such as optineurin, and nuclear dot protein 52.ConclusionPNS enhanced the PINK1/Parkin pathway and facilitated mitophagy in the hippocampus, thereby preventing cerebral oxidative stress in SAMP8 mice. This may be a mechanism contributing to the cognition-improvement effect of PNS.

Chronic Treatment with Melatonin Improves Hippocampal Neurogenesis in the Aged Brain and Under Neurodegeneration.

Adult hippocampal neurogenesis is altered during aging and under different neuropsychiatric and neurodegenerative diseases. Melatonin shows neurogenic and neuroprotective properties during aging and neuropathological conditions. In this study, we evaluated the effects of chronic treatment with melatonin on different markers of neurodegeneration and hippocampal neurogenesis using immunohistochemistry in the aged and neurodegenerative brains of SAMP8 mice, which is an animal model of accelerated senescence that mimics aging-related Alzheimer’s pathology. Neurodegenerative processes observed in the brains of aged SAMP8 mice at 10 months of age include the presence of damaged neurons, disorganization in the layers of the brain cortex, alterations in neural processes and the length of neuronal prolongations and β-amyloid accumulation in the cortex and hippocampus. This neurodegeneration may be associated with neurogenic responses in the hippocampal dentate gyrus of these mice, since we observed a neurogenic niche of neural stem and progenitor/precursors cells in the hippocampus of SAMP8 mice. However, hippocampal neurogenesis seems to be compromised due to alterations in the cell survival, migration and/or neuronal maturation of neural precursor cells due to the neurodegeneration levels in these mice. Chronic treatment with melatonin for 9 months decreased these neurodegenerative processes and the neurodegeneration-induced neurogenic response. Noticeably, melatonin also induced recovery in the functionality of adult hippocampal neurogenesis in aged SAMP8 mice.

Activation of the TREK-1 Potassium Channel Improved Cognitive Deficits in a Mouse Model of Alzheimer's Disease by Modulating Glutamate Metabolism.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by cognitive dysfunction. The glutamate (Glu) metabolic pathway may be a major contributor to the memory dysfunction associated with AD. The TWIK-related potassium channel-1 (TREK-1) protects against brain ischemia, but any specific role for the channel in AD remains unknown. In this study, we used SAMP8 mice as an AD model and age-matched SAMR1 mice as controls. We explored the trends of changes in TREK-1 channel activity and the levels of AD-related molecules in the brains of SAMP8 mice. We found that the expression level of TREK-1 increased before 3months of age and then began to decline. The levels of Tau and Glu increased with age whereas the acetylcholine level decreased with age. α-Linolenic acid (ALA), an activator of the TREK-1 channel, significantly increased the TREK-1 level, and improved the learning and memory deficits of SAMP8 mice aged 6months. The mechanism in play may involve the Glu metabolic pathway. After activation of the TREK-1 channel, damaged neurons and astrocytes were rescued, the levels of Glu and the N-methyl-D-aspartate receptor were downregulated, and the level of glutamate transporter-1 was upregulated. These findings suggest that TREK-1 plays a crucial role in the pathological progression of AD; activation of the TREK-1 channel improved cognitive deficits in SAMP8 mice via a mechanism that involved Glu metabolism. The TREK-1 potassium channel may thus be a valuable therapeutic target in AD patients.

Inhibition of caspase-1 ameliorates tauopathy and rescues cognitive impairment in SAMP8 mice.

The inflammasome assembles leading to increased cleavage and activity of caspase-1 and downstream IL-1β release, which plays a significant role in the pathogenesis of Alzheimer's disease (AD). Previous studies have shown that caspase-1-mediated neuroinflammation occurs early in AD process. However, the detailed role of caspase-1 in aging-related AD-like neuropathology is still unclear so far. In this study, by using SAMP8 mice, an animal model of accelerated aging, we detected the levels of caspase-1 in brains of 3-, 7-, and 11-month-old mice and observed that caspase-1 was activated during aging process. More importantly, we provided the evidence that VX-765, a selective inhibitor of caspase-1, significantly rescued spatial learning and memory impairments and reduced tau hyperphosphorylation in brains of SAMP8 mice at early stages of the disease. This amelioration might be attributed to IL-1β-induced hypoactivation of tau kinases. Our results imply that caspase-1 may represent as a potential therapeutic target for neurodegenerative tauopathies.

Kampo formulas alleviate aging-related emotional disturbances and neuroinflammation in male senescence-accelerated mouse prone 8 mice.

Aging-induced neuroinflammation, also known as neuroinflammaging, plays a pivotal role in emotional disturbances, including depression and anxiety, in older individuals, thereby leading to cognitive dysfunction. Although numerous studies have focused on therapeutic strategies for cognitive impairment in older individuals, little research has been performed on treating its preceding emotional disturbances. Here, we examined whether Kampo formulas (kososan [KS], nobiletin-rich kososan [NKS], and hachimijiogan [HJG]) can ameliorate aging-induced emotional disturbances and neuroinflammation in mice. The depression-like behaviors observed in SAMP8 mice, relative to normally aging SAMR1 mice, were significantly prevented by treatment with Kampo formulas for 13 weeks. Western blot analysis revealed that hippocampal neuroinflammation was significantly abrogated by Kampo formulas. KS and NKS also significantly attenuated the hippocampal neuroinflammatory priming induced by lipopolysaccharide (LPS, 0.33 mg/kg, i.p.) challenge in SAMP8 mice. Hippocampal IL-1β, IL-6, and MCP-1 levels were significantly decreased in NKS-treated SAMP8 mice. KS and NKS showed significantly reduced tau accumulation in the brains of SAMP8 mice. RNA-sequencing revealed that each Kampo formula led to unique dynamics of hippocampal gene expression and appeared to abrogate hippocampal inflammatory responses. HJG significantly blocked the LPS-induced increase in serum IL-6 and MCP-1. These results suggest that Kampo formulas would be useful for treating aging-induced depression, in part by regulating neuroinflammatory pathways. This finding may pave the way for the development of therapeutic strategies for aging-related emotional disturbances, which may contribute to the prevention of cognitive dysfunction in older individuals.

P14 LW-AFC treatment improves learning-memory ability and brain glucose metabolism in a mouse model of Alzheimer’s Disease

Objective: Alzheimer’s disease (AD) causes progressive hippocampus dysfunctions leading to the impairment of learning and memory ability and a reduced uptake rate of glucose in the hippocampus. LW-AFC is a new formula derived from the classical traditional Chinese medicinal prescription Liuwei Dihuang decoction. In this study, we investigated the beneficial and protective effects of LW-AFC in learning-memory ability and brain glucose metabolism in a widely used AD model, the senescence-accelerated prone mouse (SAMP8). Methods: SAMP8 mice were administrated LW-AFC (1.6 g/kg) for 2 months. The Morris water maze (MWM) test, shuttle box test, and novel object recognition test, were all used to evaluate cognition abilities. Fluorodeoxyglucose positron emission tomography (FDG-PET) was employed to detect the level of glucose uptake in the mouse brain. The concentrations of ATP, ADP and AMP were determined by HPLC. Results: The results from the MWM, shuttle box, and novel object recognition tests showed impairments in object recognition memory and spatial learning and memory, and active avoidance in SAMP8 mice. Administration of LW-AFC ameliorated the impairments in learning and memory abilities. The FDG-PET results showed a decrease in the uptake of glucose in the brains of SAMP8 mice with increasing age. LW-AFC enhanced glucose uptake in the brain of SAMP8 mice. Decreases in the concentrations of ATP, ADP and AMP were also found in the brains of SAMP8 mice. Administration of LW-AFC increased the concentration of all energy substances. Conclusion: LW-AFC could ameliorate deterioration of cognition in SAMP8 mice by improving glucose metabolism.

Fraction n-Butanol of Radix Notoginseng Protects PC12 Cells from Aβ25-35-Induced Cytotoxicity and Alleviates Cognitive Deficits in SAMP8 Mice by Attenuating Oxidative Stress and Aβ Accumulation.

Chinese medicine has been used for Alzheimer's disease (AD) treatment for thousands of years with more effective and fewer side effects. Therefore, developing effective potential candidates from Chinese medicine against AD would be considered as critical and efficient therapy for AD treatment. This study was designed to evaluate the neuronal protective effect of fraction n-butanol (NB) of Radix Notoginseng on Aβ25–35-induced PC12 cells, explore the effect of the tested fraction on spatial learning and memory, and characterize the impacts of fraction NB on antioxidant enzymes, Aβ production, and APP and BACE1 expressions. The results revealed that fraction NB could promote proliferation of PC12 cells and protect and rescue PC12 cells from Aβ25–35-induced cell death. Moreover, fraction NB could improve spatial learning and memory impairments of senescence-accelerated prone8 (SAMP8) mice and attenuate oxidative stress and reduce the production of Aβ by inhibiting the expressions of APP and BACE1 in the brains of SAMP8 mice. The result of single dose acute toxicity assay showed that fraction NB had a mild toxicity in vivo. The pronounced actions against AD and in vivo low toxicity of fraction NB suggest that fraction NB may be a useful alternative to the current AD treatment.

Neuroprotective Properties of Panax notoginseng Saponins via Preventing Oxidative Stress Injury in SAMP8 Mice.

Inhibiting oxidative damage in early stage of Alzheimer's disease (AD) is considered as a strategy for AD treatment. Our previous study has shown that Panax notoginseng saponins (PNS) have an antiaging action by increasing the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) in the serum of aged rats. In this study, we aimed to investigate the effects of PNS on antioxidant enzymes and uncoupling proteins (UCPs) involved in oxidative stress in AD mice. The results showed that PNS prevented neuronal loss in hippocampal CA1 region and alleviated pathomorphological change of neurons in CA1 region. Moreover, PNS inhibited the production of 8-hydroxydeoxyguanosine (8-OHdG), enhanced the expressions and activities of SOD, CAT, and GSH-PX, and improved the mRNA and protein levels of UCP4 and UCP5 in the brains of SAMP8 mice. Together, our study shows that PNS has the ability to protect neurons in AD brain from oxidative stress damage through attenuating the production of 8-OHdG, enhancing the activities of antioxidant enzymes and the expressions levels of UCP4 and UCP5. Accordingly, PNS may be a promising agent for AD treatment.

Effect of Panax notoginseng saponins on expression of α-secretase mRNA in brains of senescence-accelerated SAMP8 mice

To study the effect of Panax notoginseng saponins (PNS) on expression of alpha-aecretase mRNA in the brains of senescence-accelerated SAMP8 mice. SAMP8 mice were randomly divided into the control group, the PNS high-dosage group (200 mg x kg(-1)), the PNS low-dosage group (100 mg x kg(-1)) and the huperzine A group (0.3 mg x kg(-1)), with eight mice in each group. The control group and each administration group were orally administered with the same volume of double distilled water once for consecutively two months. The expression of alpha-secretase (ADAM 9, ADAM10, ADAM17) mRNA was assayed by real-time fluorescence quantitative polymerase chain reaction (Real-time PCR). The expression of ADAM9 mRNA in PNS high-dosage group and huperzine A group were significantly higher than that of the control group (P < 0.05). The expression of ADAM10 in the PNS high-dosage group, the PNS low-dosage group and the huperzine A group showed no significant difference from the control group. PNS can up-regulate expressions of ADAM9 mRNA and down-regulate expressions of ADAM10 mRNA in the brains of SAMP8 mice.

The Increase of D-Amino Acids in Alzheimer′s Disease-Related Proteins Isolated from the Brains of SAMP8 Mice

これまで、生物を構成するアミノ酸はL-体が主体であると考えられてきた。しかし近年、L-アミノ酸の光学異性体であるD-アミノ酸の生体内での機能が明らかになりつつある。本研究では、加齢とともに発症リスクの高まるアルツハイマー病に注目し、アルツハイマー病関連タンパク質に含有されるD-アミノ酸の加齢に伴う量の変化を解析した。実験にはアルツハイマー病のモデル動物である老化促進モデル動物SAMP８系統（SAMP8）を用いた。加齢の進んだSAMP8大脳から抽出したアルツハイマー病関連タンパク質のうち、タンパク質脱リン酸化酵素であるPP1CにおいてD-アスパラギン酸とD-セリンの量が増加していることが明らかになった。PP1Cはアルツハイマー病の原因分子のひとつであるTauの脱リン酸化作用を持つことから、D-アミノ酸含有PP1Cの生理活性低下と、アルツハイマー病との間に何らかの関連性があることが示唆された。

Dysfunction of astrocytes in senescence‐accelerated mice SAMP8 reduces their neuroprotective capacity

Early onset increases in oxidative stress and tau pathology are present in the brain of senescence-accelerated mice prone (SAMP8). Astrocytes play an essential role, both in determining the brain's susceptibility to oxidative damage and in protecting neurons. In this study, we examine changes in tau phosphorylation, oxidative stress and glutamate uptake in primary cultures of cortical astrocytes from neonatal SAMP8 mice and senescence-accelerated-resistant mice (SAMR1). We demonstrated an enhancement of abnormally phosphorylated tau in Ser(199) and Ser(396) in SAMP8 astrocytes compared with that of SAMR1 control mice. Gsk3beta and Cdk5 kinase activity, which regulate tau phosphorylation, was also increased in SAMP8 astrocytes. Inhibition of Gsk3beta by lithium or Cdk5 by roscovitine reduced tau phosphorylation at Ser(396). Moreover, we detected an increase in radical superoxide generation, which may be responsible for the corresponding increase in lipoperoxidation and protein oxidation. We also observed a reduced mitochondrial membrane potential in SAMP8 mouse astrocytes. Glutamate uptake in astrocytes is a critical neuroprotective mechanism. SAMP8 astrocytes showed a decreased glutamate uptake compared with those of SAMR1 controls. Interestingly, survival of SAMP8 or SAMR1 neurons cocultured with SAMP8 astrocytes was significantly reduced. Our results indicate that alterations in astrocyte cultures from SAMP8 mice are similar to those detected in whole brains of SAMP8 mice at 1-5 months. Moreover, our findings suggest that this in vitro preparation is suitable for studying the molecular and cellular processes underlying early aging in this murine model. In addition, our study supports the contention that astrocytes play a key role in neurodegeneration during the aging process.

Scrapie infection activates the replication of ecotropic, xenotropic, and polytropic murine leukemia virus (MuLV) in brains and spinal cords of senescence-accelerated mice: Implication of MuLV in progression of scrapie pathogenesis

Senescence-accelerated mice (SAMP8) have a short life span, whereas SAMR1 mice are resistant to accelerated senescence. Previously it has been reported that the Akv strain of ecotropic murine leukemia virus (E-MuLV) was detected in brains of SAMP8 mice but not in brains of SAMR1 mice. In order to determine the change of MuLV levels following scrapie infection, we analyzed the E-MuLV titer and the RNA expression levels of E-MuLV, xenotropic MuLV, and polytropic MuLV in brains and spinal cords of scrapie-infected SAM mice. The expression levels of the 3 types of MuLV were increased in scrapie-infected mice compared to control mice; E-MuLV expression was detected in infected SAMR1 mice, but only in the terminal stage of scrapie disease. We also examined incubation periods and the levels of PrP Sc in scrapie-infected SAMR1 (sR1) and SAMP8 (sP8) mice. We confirmed that the incubation period was shorter in sP8 (210 ± 5 days) compared to sR1 (235 ± 10 days) after intraperitoneal injection. The levels of PrP Sc in sP8 were significantly greater than sR1 at 210 ± 5 days, but levels of PrP Sc at the terminal stage of scrapie in both SAM strains were virtually identical. These results show the activation of MuLV expression by scrapie infection and suggest acceleration of the progression of scrapie pathogenesis by MuLV.

Scrapie strain-specific interactions with endogenous murine leukaemia virus.

The finding that a senescence-accelerated mouse (SAMP8) shows early brain ageing, with histopathological changes resembling those seen in scrapie, combined with the discovery of high levels of endogenous murine leukaemia virus (MuLV) in brains of SAMP8 mice prompted us to examine the effect of scrapie infection on MuLV titres in this strain and in one of its progenitors, the AKR strain. Three scrapie strains (ME7, 22L and 139A) that had a comparatively short incubation period in SAMP8 and AKR mice caused an increase in brain MuLV titres that was scrapie strain-specific: in each mouse strain, the greatest effect was with 1 39A, and the least with ME7. The 22A scrapie strain, which has a long incubation period in SAMP8 mice, did not affect MuLV titres in brains of this mouse strain. Previous analyses of scrapie incubation periods in AKR, SAMP8 and another strain derived from an AKR cross (SAMR1) showed an inverse relationship between brain MuLV titres and scrapie incubation periods. This finding, combined with the effect of scrapie on MuLV titres, suggests an interaction between the scrapie infectious process and MuLV replication.