SAMP8 Mice Research Articles

MiR-23b-3p rescues cognition in Alzheimer’s disease by reducing tau phosphorylation and apoptosis via GSK-3β signaling pathways

Dysregulated microRNA (miRNA) expression in the brain can contribute to cognitive dysfunction and aberrant tau hyperphosphorylation in Alzheimer’s disease (AD). Several studies have reported a role for microRNA-23b-3p (miR-23b-3p) in various neurologic disorders; however, its involvement in cognition-related functions remains unclear. In the present study, we investigated the potential therapeutic effects and mechanisms of miR-23b-3p in AD. miRNA profiles in the cortex of amyloid precursor protein (APP)/presenilin 1 (PS1) double transgenic mice (APP/PS1 mice) demonstrated that miR-23b-3p was reduced. This decrease was verified in APPswe cells, SAMP8 mouse brains, and plasma from AD patients. Furthermore, glycogen synthase kinase-3β (GSK-3β), a major tau kinase implicated in tau pathology, was identified as a target of miR-23b-3p. Functional in vivo studies demonstrated that intracerebroventricular delivery of miR-23b-3p in APP/PS1 mice ameliorated cognitive deficits, histopathological changes, and tau phosphorylation immunoreactivity at several sites by inhibiting GSK-3β expression and activation. Similarly, the upregulation of miR-23b-3p in APPswe cells inhibited GSK-3β-mediated tau hyperphosphorylation, Aβ1-42 generation, and neuronal apoptosis, resulting in the suppression of the GSK-3β/p-tau and Bax/caspase-3 pathways. Collectively, our findings strongly support the hypothesis that miR-23b-3p plays a neuroprotective role in AD, thereby identifying miR-23b-3p as a promising therapeutic target for AD.

Astaxanthin delays brain aging in senescence-accelerated mouse prone 10: inducing autophagy as a potential mechanism

ABSTRACT Brain aging is a complex biological process often associated with a decline in cognitive functions and motility. Astaxanthin (AST) is a strong antioxidant capable of crossing the blood–brain barrier. The effect of AST on brain aging and its physiological and molecular mechanism are still unclear. The study aimed to investigate whether AST from AstaReal A1010 improved brain aging by inducing autophagy in SAMP10 mice. Different concentrations of AstaReal A1010 were intragastrically administered to 6-month-old SAMP10 mice for 3 months. The results demonstrated that AST delayed age-related cognitive decline, motor ability and neurodegeneration, upregulated the expression levels of autophagy-related genes beclin-1 and LC3 in the brain. It may induce autophagy by regulating IGF-1/Akt/mTOR and IGF-1/Akt/FoxO3a signaling. Treatment with autophagy inhibitor 3-methyladenine (3MA) partly reversed the anti-aging effect of AST. In conclusion, our findings suggest that AST may induce autophagy by regulating IGF-1/Akt/mTOR and IGF-1/Akt/FoxO3a signaling, thereby delaying age-related neurodegeneration and cognitive decline in SAMP10 mice.

Mitochondrial homeostasis is involved in inhibiting hippocampus neuronal apoptosis during ZSWF ameliorate the cognitive dysfunction of SAMP8 mice

• ZSWF could inhibit neuronal apoptosis and improve cognitive ability of SAMP8 mice. • ZSWF could simultaneously regulate mitophagy and mitochondrial biogenesis. • ZSWF improve cognitive ability by maintaining neural mitochondrial homeostasis. ZSWF, a traditional Chinese medicine and nutritional supplement for nourishing kidney, presents ameliorating cognitive deficits effect. However, its mechanism remains unclear. Imbalance of neural mitochondrial homeostasis is a pathogenesis of AD. Considering “tonify kidney and nourish encephala” in traditional Chinese medicine theory is consistent with “mitochondria provides energy for neuros to maintain brain activity”, we hypothesized whether ZSWF could improve cognitive ability by regulating neuronal mitochondrial homeostasis. In this study, we firstly confirmed that ZSWF could improve the cognitive function of SAMP8 mice, alleviate histopathological lesion and inhibit neuro apoptosis. Then the components of ZSWF in cerebrospinal fluid and hippocampus were identified to fish their potential targets, which further indicated ZSWF might regulate mitochondrial homeostasis. Experimentally, we verified that ZSWF could reverse the neuronal mitochondrial loss of SAMP8 mice by upregulating PINK1, Parkin and PGC-1α to simultaneously regulate mitophagy and mitochondrial biogenesis to maintain mitochondrial homeostasis.

Trimethylamine N-oxide (TMAO) drives insulin resistance and cognitive deficiencies in a senescence accelerated mouse model

It has been established that ageing is the major risk factor for cognitive deficiency and it is becoming increasingly evident that insulin resistance is another factor. Biological plausibility for a link between insulin resistance and dementia is relevant for understanding disease etiology, and to form bases for prevention efforts to decrease disease burden. In the present study, peripheral and central insulin resistance was found in SAMP8 mice (aging mouse model) accompanied by cognitive deficiencies. Furthermore, a marked peripheral inflammatory state was observed in SAMP8 mice, followed by neuroinflammation that could be due to a higher cytokine leaking into the brain across an aging-disrupted blood brain barrier. Moreover, aging-induced gut dysbiosis produces higher TMAO that could also contribute to the peripheral and central inflammatory tone as well as to the cognitive deficiencies observed in SAMP8 mice. All those alterations were reversed by DMB, a treatment that decreases TMAO levels. Data obtained from this project suggest that microbial dysbiosis and increased TMAO secretion could be a key link between aging, insulin resistance and dementia. Thus, pharmacological intervention that leads to decreased TMAO levels, such as DMB, could open a new avenue for the future treatment of neurodegenerative diseases.

Gosha-jinki-Gan (GJG) shows anti-aging effects through suppression of TNF-α production by Chikusetsusaponin V.

Frailty develops due to multiple factors, such as sarcopenia, chronic pain, and dementia. Go-sha-jinki-Gan (GJG) is a traditional Japanese herbal medicine used for age-related symptoms. We have reported that GJG improved sarcopenia, chronic pain, and central nervous system function through suppression of tumor necrosis factor-alpha (TNF-α) production. In the present study, GJG was found to reduce the production of TNF-α in the soleus muscle of senescence-accelerated mice at 12weeks and 36weeks. GJG did not change the differentiation of C2C12 cells with 2% horse serum. GJG significantly decreased the expression of Muscle atrophy F-box protein (MAFbx) induced by TNF-α in C2C12 cells on real-time PCR. TNF-α significantly decreased the expression of PGC-1α and negated the enhancing effect of GJG for the expression of PGC-1α on digital PCR. Examining 20 chemical compounds derived from GJG, cinnamaldehyde from cinnamon bark and Chikusetsusaponin V (CsV) from Achyrantes Root dose-dependently decreased the production of TNF-⍺ in RAW264.7 cells stimulated by LPS. CsV inhibited the nuclear translocation of nuclear factor-kappa B (NF-κB) p65 in RAW264.7 cells. CsV showed low permeability using Caco-2 cells. However, the plasma concentration of CsV was detected from 30min to 6h and peaked at 1h in the CD1 (ICR) mice after a single dose of GJG. In 8-week-old SAMP8 mice fed 4% (w/w) GJG from one week to four weeks, the plasma CsV concentration ranged from 0.0500 to 10.0ng/mL. The evidence that CsV plays an important role in various anti-aging effects of GJG via suppression of TNF-⍺ expression is presented.

Extract of Corallodiscus flabellata attenuates renal fibrosis in SAMP8 mice via the Wnt/\u03b2-catenin/RAS signaling pathway

BackgroundFibrosis is one of the most common pathological features of the aging process of the kidney, and fibrosis in aging kidneys also aggravates the process of chronic kidney disease (CKD). Corallodiscus flabellata B. L. Burtt (C. flabellata, CF) is a commonly used botanical drug in Chinese folklore. However, few studies have reported its pharmacological effects. This study aimed to explore the effect of CF ethanol extract on renal fibrosis in SAMP8 mice and identify potentially active compounds.MethodsSenescence-accelerated mouse-prone 8 (SAMP8) were used as animal models, and different doses of CF were given by gavage for one month. To observe the degree of renal aging in mice using β-galactosidase staining. Masson staining and the expression levels of Col-I, α-SMA, and FN were used to evaluate the renal fibrosis in mice. The protein expression levels of Nrf2 pathway and Wnt/β-catenin/RAS pathway in the kidney were measured. And β-galactosidase (β-gal) induced NRK-52E cells as an in vitro model to screen the active components of CF.ResultsThe CF ethanol extract significantly inhibited the activity of renal β-galactosidase and the expression levels of Col-I, α-SMA, and FN in SAMP8 mice, and improved Masson staining in SAMP8 mice. CF remarkably reduced urinary protein, creatinine, urea nitrogen and serum levels of TNF-α and IL-1β in SAMP8 mice, and significantly increased the levels of SOD and GSH-Px. Moreover, CF activated the Nrf2 pathway and blocked the Wnt/β-catenin/RAS pathway in the kidneys of mice. Besides, 3,4-dihydroxyphenylethanol (SDC-0-14, 16) and (3,4-dihydroxyphenylethanol-8-O-[4-O-trans-caffeoyl-β-D-apiofuranosyl-(1→3)-β-D-glucopyranosyl (1→6)]-β-D-glucopyranoside (SDC-1-8) were isolated from CF, which reduced the senescence of NRK-52E cells, and maybe the active ingredients of CF playing the anti-aging role.ConclusionsOur experiments illuminated that CF ethanol extract may ameliorate renal fibrosis in SAMP8 mice via the Wnt/β-catenin/RAS pathway. And SDC-0-14,16 and SDC-1-8 may be the material basis for CF to exert anti-renal senescence-related effects.

Administration of miR-195 Inhibitor Enhances Memory Function Through Improving Synaptic Degradation and Mitochondrial Dysfunction of the Hippocampal Neurons in SAMP8 Mice.

Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD) and miR-195 is involved in mitochondrial disorder through targeting MFN-2 protein in hippocampal neurons of AD. To clarify if administration of miR-195 inhibitor could enhance the memory deficits through improving hippocampal neuron mitochondrial dysfunction in SAMP8 mice. The expression of miR-195 was detected by RT-qPCR in primary hippocampal neurons and HT-22 cells treated with Aβ1-42. Morris water maze (MWM) was used to assess the learning and memory function in SAMP8 mice administrated with antagomir-195. Transmission electron microscopy was employed to determine the morphological changes of synapses and mitochondria of hippocampus in SAMP8 mice. Mitochondrial respiration was measured using a high-resolution oxygraph. The expression of miR-195 were upregulated in the primary hippocampal neurons and HT-22 cells induced by Aβ1-42. Inhibition of miR-195 ameliorated the mitochondrial dysfunction in HT-22 cells induced by Aβ1-42, including mitochondrial morphologic damages, mitochondrial membrane potential, respiration function, and ATP production. Administration of antagomir-195 by the third ventricle injection markedly ameliorated the cognitive function, postsynaptic density thickness, length of synaptic active area, mitochondrial aspect ratio, and area in hippocampus of SAMP8 mice. Finally, antagomir-195 was able to promote an increase in the activity of respiratory chain complex CI and II in SAMP8 mice. This study demonstrated that miR-195 inhibitor ameliorated the cognitive impairment of AD mice by improving mitochondrial structure damages and dysfunction in the hippocampal neurons, which provide an experimental basis for further exploring the treatment strategy of AD.

Dasatinib plus quercetin attenuates some frailty characteristics in SAMP10 mice

Senolytics are a class of drugs that selectively remove senescent cells. Dasatinib and quercetin have been discovered, and their combination has shown various anti-ageing effects. The SAMP10 mouse strain is a model of brain ageing. Here, we investigated the effect of combination on frailty characteristics in SAMP10. By comparing SAMP10 with SAMR1 mice as normal ageing controls, we investigated some frailty characteristics. Frailty was assessed at 18–38 weeks of age with a clinical frailty index. Motor and cognitive function of these mice were evaluated using behavioral experiments. SAMP10 mice were divided into vehicle and combination, and these functions and histological changes in the brain hippocampus were investigated. Finally, the in vitro effects of combination on oxidative stress-induced senescent muscle and neuronal cells were investigated. As a result, we found that frailty index was higher in SAMP10 than SAMR1. Motor and cognitive function were worse in SAMP10 than SAMR1. Furthermore, combination therapy improved frailty, motor and cognitive function, and the senescent phenotype of the hippocampus compared with vehicle in SAMP10. In summary, SAMP10 showed more marked frailty characteristics than SAMR1, and dasatinib and quercetin attenuated them in SAMP10. From our results, senolytic therapy might contribute protective effects against frailty.

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.

Effect of electroacupuncture on hepatocyte autophagy and oxidative stress in SAMP8 mice by regulating AMPK/mTOR/ULK1 signaling pathway

To observe the effect of electroacupuncture (EA) on physical strength and expression levels of hepatic AMP-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), unc-51 like autophagy activating kinase 1 (ULK1) proteins and Atg5, Atg7, Atg13, Beclin1 and ULK1 mRNAs in aging (senescence accelerated mouse/prone 8, SAMP8)mice, so as to exp lore its mechanism underlying delaying aging by activating AMPK/mTOR/ULK1 signaling pathway. Twenty-four male SAMP8 mice were randomly divided into model group, rapamycin (autophagy inducer) group, EA group and EA+autophagy inhibitor (EA+inhibitor) group, with 6 mice in each group, and 6 homologous anti-rapid aging male (SAMR1) mice in the same age were used as the control group. Mice of the rapamycin group received intraperitoneal injection of rapamycin solution (2 mg·kg-1·d-1). EA (2 Hz, 1 mA) was applied to bilateral "Taichong"(LR3)and "Shenshu"(BL23) for 15 min each time. Mice of the EA+inhibitor group received intraperitoneal injection of mTOR inhibitor 3-methyladenine (1.5 mg·kg-1·d-1) before the EA intervention each time. The above-mentioned interventions were conducted 6 times a week for 2 consecutive weeks. Physical conditions of mice were assessed by exhaustive swimming tests. Histopathological changes of the liver were observed by H.E. staining. Western blot was used to detect the expression of AMPK, phosphorylated AMPK (p-AMPK), mTOR, phosphorylated mTOR (p-mTOR), ULK1 and phosphorylated ULK1 (p-ULk1) in the liver tissues. The expression levels of Atg5, Atg7, Atg13, Beclin1 and ULK1 (cellular autophagy-related genes) mRNAs in the liver were detected by quantitative real-time PCR. The immunoactivity (IA) of heme oxygenase 1 (HO-1) in the liver was detected by immunohistochemistry, and the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA) of the liver were measured by hydroxylamine method for assessing the level of oxidative stress. Compared with the control group, the duration of exhaustive swimming, the expression levels of AMPK, p-AMPK, ULK1 and p-ULK1 proteins, and Atg5, Atg7, Atg13, Beclin1 and ULK1 mRNA, HO-1 IA and SOD activity were considerably down-regulated (P<0.01), while the expression levels of mTOR and p-mTOR and MDA content were significantly up-regulated (P<0.01) in the model group. In comparison with the model group, the duration of the exhausted swimming, the expression levels of AMPK, p-AMPK, ULK1 and p-ULK1 proteins, and Atg5, Atg7, Atg13, Beclin1 and ULK1 mRNAs, HO-1 IA and SOD activity were significantly up-regulated (P<0.01, P<0.05), whereas the expression levels of mTOR and p-mTOR proteins and MDA content were notably down-regulated (P<0.01, P<0.05) in the rapamycin, EA and EA+inhibitor groups. The improvement of the abovementioned indexes of EA+inhibitor group was not as good as rapamycin and EA groups (P<0.01), suggesting an elimination of the therapeutic effects after administration of 3-methyladenine. No significant differences were found between the rapamycin and EA groups in the abovementioned indexes (P>0.05) except p-mTOR and mTOR which were higher in the EA group (P<0.01). H.E. staining showed ambiguous boundary of the liver lobule, disordered arrangement of hepatocytes with a large amount of fat vacuoles at different size and deviation of nucleus, and lysis of some hepatocytes. These situations were relatively milder in the rapamycin and EA groups. EA may enhance physical strength and promote cellular autophagy in the liver of aging mice by regulating AMPK/mTOR/ULK1 signaling, thereby inhibiting excessive oxidative stress, and delaying aging process to some extent.

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.

老化促進モデルSAMP8マウスの社会的認知障害とarginase-1発現に対する八味地黄丸の効果

老化促進モデルSAMP8マウスの社会的認知障害とarginase-1発現に対する八味地黄丸の効果

Perspective on the relationship between microbiota dysbiosis and neuroinflammation: probiotics as a treatment option.

Perspective on the relationship between microbiota dysbiosis and neuroinflammation: probiotics as a treatment option.

Repetitive Transcranial Magnetic Stimulation Reduces Neuronal Loss and Neuroinflammation in Parkinson?s Disease Through the miR-195a-5p/CREB Axis.

To elucidate the molecular mechanism underlying the repetitive transcranial magnetic stimulation (rTMS) -induced improvement in Parkinson's disease (PD). We established a PD model by administering 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to SAMP8 mice. The mice were then subjected to rTMS. Motor coordination and cognition were assessed using rotarod and Morris water maze tests, respectively. Nissl staining was performed to evaluate neuronal apoptosis. Furthermore, western blotting was employed to assess the expression of tyrosine hydroxylase and brain-derived neurotrophic factor. Additionally, the levels of tumor necrosis factor-α, interferon-γ, and interleukin-6 in the cerebrospinal fluid were evaluated using specific enzyme-linked immunosorbent assay kits. The expression of miR-195a-5p and cyclic AMP-response element-binding protein (CREB) was examined using quantitative real-time polymerase chain reaction and western blotting. Dual-luciferase reporter assay was performed using primary cortical rat neurons to validate the interaction between miR-195a-5p and CREB. rTMS improved cognition and motor coordination as well as reduced neuronal apoptosis/ and the levels of inflammatory factors in PD mice. It downregulated the expression of miR-195a-5p but upregulated that of CREB. In primary rat cortical neurons, miR-195a-5p directly targeted CREB, and we found that miR-195a-5p suppression enhanced cognitive and motor functions in PD mice. Moreover, miR-195a-5p downregulation decreased inflammatory response and neuronal loss in the PD mice. rTMS exerted its neuroprotective effects on PD mice by regulating the miR-195a-5p/CREB axis. This finding reveals a novel mechanism through which rTMS improves PD and indicates that miR-195a-5p is a potential therapeutic target for PD treatment.

RTMS alleviates AD-induced cognitive impairment by inhibitng apoptosis in SAMP8 mouse.

This study sought to investigate whether repetitive transcranial magnetic stimulation (rTMS) could alleviate cognitive dysfunction in SAMP8 mice by reducing cell apoptosis and activating the cAMP/PKA/CREB signalling pathway. A total of 40 SAMP8 mice were randomly assigned to the SAMP8 group (n=20), and rTMS treatment group (rTMS+SAMP8, n=20); additionally, 20 homologous and normal aged SAMR1 mice were used as the control group(n=20). The Morris water maze and Y maze tests were applied to evaluate spatial learning and memory ability. Haematoxylin and eosin (HE) staining and terminal-deoxynucleotidyl transferase-mediated nick end labelling (TUNEL) were used to observe the changes in neurons in the cortex and hippocampus. Western blotting and RT-PCR were used to detect signalling related proteins. rTMS significantly improved spatial learning and memory deficits and morphological abnormalities in the hippocampus region of the hippocampus. In addition, rTMS reduced apoptosis of neurons caused by AD and the expression of pro-apoptotic proteins (Caspase-3 and Bax) and increased the expression of an antiapoptotic protein (Bcl-2). Furthermore, rTMS activated the cAMP/PKA/CREB signalling pathway. These results showed that rTMS could ameliorate cognitive deficits in AD mice by inhibiting apoptosis via activation the cAMP/PKA/CREB signalling pathway.

Cannabidiol (CBD) improves cognition and decreases anxiety in the SAMP8 mouse model of Alzheimer’s

The use of cannabidiol (CBD) has grown rapidly over the last few years. CBD has been purported to work on a range of conditions, including anxiety, pain, and psychosis. There has been recent interest in CBD as a treatment for age-related cognitive disorders due to its antioxidant and anti-inflammatory properties. Here, we tested the effects of chronic CBD administration on learning and memory in the SAMP8 mouse model of Alzheimer's disease. SAMP8 mice develop an age-related impairment in learning and memory which corresponds to an increase in amyloid-β (Aβ), hyperphosphorylated tau, oxidative stress, impaired efflux of Aβ across the blood-brain barrier and neuroinflammation. SAMP8 mice starting at 11 months of age were treated with CBD (0, 3 or 30 mg/kg) daily via oral administration for 60 days. A 3 month old SAMP8 group receiving vehicle served as an unimpaired control. After 30 days of treatment, learning and memory (T-maze and novel object recognition), activity in open field, anxiety in the elevated plus maze, and strength were assessed. At the end of behavioral testing brains were collected for analysis. Mice which received CBD 30 mg/kg had significant improvement in learning and memory in the T-maze, taking fewer trials to reach criterion than 12 month old vehicle treated mice. CBD improved novel object recognition memory of 12 month old SAMP8 mice, which spent significantly more time with the novel object in the 24-hour retention test than the age-matched vehicle treated controls. While there was no difference in total distance traveled measured by open field activity, the mice that that received CBD displayed decreased anxiety at both 3 and 30 mg/kg/day doses compared to the age-matched control. The mice that received 3 mg/kg/day had significantly less anxiety than the young control group. CBD had no significant effects on the measures of strength in the aged mice. Analysis of brain tissue indicate that CBD significantly decreased markers of oxidative stress. Our results indicate that CBD improves both spatial and recognition memory and decreases anxiety. The actions appear to be primarily through its antioxidant properties. CBD is a potential treatment for age-related dementia.

Learning deficits occurs prior to memory retrieval impairment in female Senescence Accelerated Mouse (SAMP8)

AbstractBackgroundThe most regularly used mouse models of Alzheimer's disease in drug development include APP/PS1, 3xTg, and 5xFAD mice. This is a limitation as all these mice represent familial AD. Given sporadic AD accounts for the majority of the AD cases in human, there is an unmet need to validate potential rodent models to better represent sporadic AD. SAMP8 is a naturally‐occurring mouse line that displays many characteristics identified in Alzheimer’s disease (AD) patients, such as learning and memory deficits, and accumulation of beta‐amyloid. In people with preclinical AD, deficits in learning manifest faster than decline in memory retrieval. It is unclear if SAMP8 mice also exhibit this feature, and therefore the current study aims to determine if this feature can be observed in SAMP8, to support the use of SAMP8 as a mouse model of sporadic AD for drug development.MethodThe cognitive function of SAMP8 mice and their age‐matched non‐AD control SAMR1 mice (at various ages) were assessed using Y maze spatial memory test, with 3‐10 min training duration and 1.5‐3 h interval between training and testing session.ResultAt 3‐4 months old, SAMP8 but not SAMR1 failed to differentiate the novel arm from familiar arm in a standard Y maze test (3 min training, 3 h interval). When training time was increased to 10 min, SAMP8 passed the test, while increased training time did not affect the performance of SAMR1 mice. These data indicated that longer training time is required by SAMP8 than SAMR1 to achieve the expected performance, suggesting the presence of learning deficits in SAMP8. Interestingly, at 6‐7 months old, though both SAMP8 and SAMR1 received 10‐min training, only SAMR1 passed the test. The performance of SAMP8 mice was successfully improved by shortening the interval between training and testing (from 3 h to 1.5 hr). These data indicate a deteriorated memory retention capability and a possible impairment in memory retrieval in SAMP8.ConclusionOverall, this study has provided supportive evidence that learning deficits occurs prior to memory retrieval impairment in SAMP8, and the use of SAMP8 as mouse model for AD.

Probiotic supplementation attenuates age-related sarcopenia via the gut-muscle axis in SAMP8 mice.

BackgroundAge‐related muscle dysfunctions are common disorders resulting in poor quality of life in the elderly. Probiotic supplementation is a potential strategy for preventing age‐related sarcopenia as evidence suggests that probiotics can enhance muscle function via the gut–muscle axis. However, the effects and mechanisms of probiotics in age‐related sarcopenia are currently unknown. In this study, we examined the effects of Lactobacillus casei Shirota (LcS), a probiotic previously reported to improve muscle function in young adult mice.MethodsWe administered LcS (1 × 108 or 1 × 109 CFU/mouse/day) by oral gavage to senescence‐accelerated mouse prone‐8 mice for 12 weeks (16‐ to 28‐week‐old). Sixteen‐week‐old and 28‐week‐old SMAP8 mice were included as non‐aged and aged controls, respectively. Muscle condition was evaluated using dual‐energy X‐ray absorptiometry for muscle mass, holding impulse and grip strength tests for muscle strength, and oxygen consumption rate, gene expressions of mitochondrial biogenesis, and mitochondrial number assays for mitochondria function. Inflammatory cytokines were determined using enzyme‐linked immunosorbent assay. Gas chromatography–mass spectrometry was utilized to measure the short‐chain fatty acid levels. The gut microbiota was analysed based on the data of 16S rRNA gene sequencing of mouse stool.ResultsThe LcS supplementation reduced age‐related declines in muscle mass (>94.6%, P < 0.04), strength (>66% in holding impulse and >96.3% in grip strength, P < 0.05), and mitochondrial function (P < 0.05). The concentration of short‐chain fatty acids (acetic, isobutyric, butyric, penic, and hexanoic acid) was recovered by LcS (>65.9% in the mice given high dose of LcS, P < 0.05) in the aged mice, and LcS attenuated age‐related increases in inflammation (P < 0.05) and reactive oxygen species (>89.4%, P < 0.001). The high dose of LcS supplementation was also associated with distinct microbiota composition as indicated by the separation of groups in the beta‐diversity analysis (P = 0.027). LcS supplementation altered predicted bacterial functions based on the gut microbiota. Apoptosis (P = 0.026), p53 signalling (P = 0.017), and non‐homologous end‐joining (P = 0.031) were significantly reduced, whereas DNA repair and recombination proteins (P = 0.043), RNA polymerase (P = 0.008), and aminoacyl‐tRNA biosynthesis (P = 0.003) were increased. Finally, the genera enriched by high‐dose LcS [linear discriminant analysis (LDA) score > 2.0] were positively correlated with healthy muscle and physiological condition (P < 0.05), while the genera enriched in aged control mice (LDA score > 2.0) were negatively associated with healthy muscle and physiological condition (P < 0.05).Conclusions Lactobacillus casei Shirota represents an active modulator that regulates the onset and progression of age‐related muscle impairment potentially via the gut–muscle axis.

Embryonal erythropoiesis and aging exploit ferroptosis

Ferroptosis is a form of regulated cell necrosis, as a consequence of Fe(II)-dependent lipid peroxidation. Although ferroptosis has been linked to cancer cell death, neurodegeneration and reperfusion injury, physiological roles of ferroptosis have not been elucidated to date mostly due to the lack of appropriate methodologies. Here, we show that 4-hydroxy-2-nonenal (HNE)-modified proteins detected by a HNEJ-1 mouse monoclonal antibody is a robust immunohistochemical technology to locate ferroptosis in tissues in combination with morphological nuclear information, based on various models of ferroptosis, including erastin-induced cysteine-deprivation, conditional Gpx4 knockout and Fe(II)-dependent renal tubular injury, as well as other types of regulated cell death. Specificity of HNEJ-1 with ferroptosis was endorsed by non-selective identification of HNE-modified proteins in an Fe(II)-dependent renal tubular injury model. We further comprehensively searched for signs of ferroptosis in different developmental stages of Fischer-344 rats from E9.5–2.5 years of age. We observed that there was a significant age-dependent increase in ferroptosis in the kidney, spleen, liver, ovary, uterus, cerebellum and bone marrow, which was accompanied by iron accumulation. Not only phagocytic cells but also parenchymal cells were affected. Epidermal ferroptosis in ageing SAMP8 mice was significantly promoted by high-fat or carbohydrate-restricted diets. During embryogenesis of Fischer-344 rats, we found ferroptosis in nucleated erythrocytes at E13.5, which disappeared in enucleated erythrocytes at E18.5. Administration of a ferroptosis inhibitor, liproxstatin-1, significantly delayed erythrocyte enucleation. Therefore, our results demonstrate for the first time the involvement of ferroptosis in physiological processes, such as embryonic erythropoiesis and aging, suggesting the evolutionally acquired mechanism and the inevitable side effects, respectively.

Donepezil improves vascular function in a mouse model of Alzheimer's disease.

Cardiovascular complications in Alzheimer's disease (AD) patients can occur years to decades prior to the onset of clinical symptoms of the disease. Donepezil represents the most effective drug in the treatment of AD. However, the potential effect of donepezil on vascular function and structure remains largely unexplored. Here, we assessed the impact of donepezil on the vascular phenotype of an established model of accelerated senescence that develops spontaneously AD, the SAMP8 mouse. Three groups of animals were included: SAMR1 (control strain), SAMP8, and SAMP8 treated with donepezil. Treatment with donepezil was administered from the 4th to the 6th month of life. At 6 months, after cognitive tests by Morris Water Maze, animals were euthanized, and their mesenteric arteries were processed for functional experiments. Untreated SAMP8 developed cognitive impairment compared to SAMR1, while donepezil treatment significantly attenuated cognitive dysfunction. SAMP8 exhibited a higher media‐to‐lumen ratio than SAMR1 and donepezil‐treated animals. Endothelial function was impaired in SAMP8 animals compared to SAMR1. The addition of vitamin C improved the vasodilatory response to acetylcholine in SAMP8. Treatment with donepezil improved endothelial function in SAMP8 animals and reduced the additional vasodilation induced by vitamin C. In conclusion, in the SAMP8 AD model, cognitive impairment is associated with endothelial dysfunction and vascular remodeling which could contribute to cardiovascular events in AD since the prodromal phases of the disease. Treatment with donepezil alleviates vascular dysfunction associated with AD through an increase in NO availability likely by counteracting inflammation and oxidative stress.