Identification of age-dependent changes in expression of senescence-accelerated mouse (SAMP8) hippocampal proteins by expression array analysis

Erinacine A-Enriched Hericium erinaceus Mycelium Delays Progression of Age-Related Cognitive Decline in Senescence Accelerated Mouse Prone 8 (SAMP8) Mice

There have been many reports on the neuroprotective effects of Hericium erinaceus mycelium, in which the most well-known active compounds found are diterpenoids, such as erinacine A. Previously, erinacine A-enriched Hericeum erinaceus mycelium (EAHEM) was shown to decrease amyloid plaque aggregation and improve cognitive disability in Alzheimer’s disease model APP/PS1 mice. However, its effects on brain aging have not yet been touched upon. Here, we used senescence accelerated mouse prone 8 (SAMP8) mice as a model to elucidate the mechanism by which EAHEM delays the aging of the brain. Three-month-old SAMP8 mice were divided into three EAHEM dosage groups, administered at 108, 215 and 431 mg/kg/BW/day, respectively. During the 12th week of EAHEM feeding, learning and memory of the mice were evaluated by single-trial passive avoidance and active avoidance test. After sacrifice, the amyloid plaques, induced nitric oxidase synthase (iNOS) activity, thiobarbituric acid-reactive substances (TBARS) and 8-OHdG levels were analyzed. We found that the lowest dose of 108 mg/kg/BW EAHEM was sufficient to significantly improve learning and memory in the passive and active avoidance tests. In all three EAHEM dose groups, iNOS, TBARS and 8-OHdG levels all decreased significantly and showed a dose-dependent response. The results indicate that EAHEM improved learning and memory and delayed degenerative aging in mice brains.

Protective Effects of Hydrolyzed Chicken Extract (Probeptigen®/Cmi-168) on Memory Retention and Brain Oxidative Stress in Senescence-Accelerated Mice

The senescence-accelerated prone (SAMP8) mouse model shows age-dependent deterioration in learning and memory and increased oxidative stress in the brain. We previously showed that healthy subjects on a six-week supplementation of a chicken meat hydrolysate (ProBeptigen®/CMI-168) demonstrated enhanced and sustained cognitive performance up until two weeks after the termination of supplementation. In this study, we investigate the effect of ProBeptigen on the progression of age-related cognitive decline. Three-month old SAMP8 mice were orally administered different doses of ProBeptigen (150,300 or 600 mg/kg/day) or saline daily for 13 weeks. Following ProBeptigen supplementation, mice showed lower scores of senescence and improved learning and memory in avoidance tasks. ProBeptigen treatment also increased antioxidant enzyme activity and dopamine level while reducing protein and lipid peroxidation and mitochondrial DNA damage in the brain. Microarray analysis of hippocampus revealed several processes that may be involved in the improvement of cognitive ability by ProBeptigen, including heme binding, insulin growth factor (IGF) regulation, carboxylic metabolic process, oxidation-reduction process and endopeptidase inhibition. Genes found to be significantly altered in both ProBeptigen treated male and female mice include Mup1, Mup17, Mup21, Ahsg and Alb. Taken together, these results suggest a potential anti-aging effect of ProBeptigen in alleviating cognitive deficits and promoting the antioxidant defense system.

Integration of heterogeneous functional genomics data in gerontology research to find genes and pathway underlying aging across species

Understanding the biological mechanisms behind aging, lifespan and healthspan is becoming increasingly important as the proportion of the world's population over the age of 65 grows, along with the cost and complexity of their care. BigData oriented approaches and analysis methods enable current and future bio-gerontologists to synthesize, distill and interpret vast, heterogeneous data from functional genomics studies of aging. GeneWeaver is an analysis system for integration of data that allows investigators to store, search, and analyze immense amounts of data including user-submitted experimental data, data from primary publications, and data in other databases. Aging related genome-wide gene sets from primary publications were curated into this system in concert with data from other model-organism and aging-specific databases, and applied to several questions in genrontology using. For example, we identified Cd63 as a frequently represented gene among aging-related genome-wide results. To evaluate the role of Cd63 in aging, we performed RNAi knockdown of the C. elegans ortholog, tsp-7, demonstrating that this manipulation is capable of extending lifespan. The tools in GeneWeaver enable aging researchers to make new discoveries into the associations between the genes, normal biological processes, and diseases that affect aging, healthspan, and lifespan.

The Effects of LW-AFC on the Hippocampal Transcriptome in Senescence-Accelerated Mouse Prone 8 Strain, a Mouse Model of Alzheimer's Disease

The senescence-accelerated mouse prone 8 (SAMP8) strain is considered a robust experimental model for developing preventative and therapeutic treatments for Alzheimer's disease (AD), a neurodegenerative disease which cannot be effectively prevented, halted, or cured. Our previous studies showed that LW-AFC, a new formula derived from the classical traditional Chinese medicinal prescription Liuwei Dihuang decoction, ameliorates cognitive deterioration in PrP-hAβPPswe/PS1ΔE9 transgenic mice and SAMP8 mice. This study aims to investigate the mechanism that mediates how LW-AFC improves cognitive deficit on the basis of the transcriptome. We conducted a genome-wide survey of gene expression in the hippocampus in mice from the senescence accelerated mouse resistant 1 (SAMR1) strain, from SAMP8 and from LW-AFC treated SAMP8. The results showed that LW-AFC reversed the transcriptome in the hippocampus of SAMP8 mice. The specific investigation of altered gene expression in subtypes defined by cognitive profiles indicated that the systemic lupus erythematosus pathway, spliceosomes, amyotrophic lateral sclerosis, and the insulin signaling were involved in the improvement of cognitive ability by LW-AFC. The expression of genes Enpp2, Etnk1, Epdr1, and Gm5900 in the hippocampus were correlated with that of LW-AFC's ameliorating cognitive impairment in SAMP8 mice. Because LW-AFC is composed of polysaccharides, glycosides, and oligosaccharides, we infer that LW-AFC has direct or indirect effects on altering gene expressions and regulating pathways in the hippocampus of SAMP8 mice. These data are helpful for the enhanced identification of LW-AFC as new therapeutic modalities to AD.

Proteomic data show an increase in autoantibodies and alpha-fetoprotein and a decrease in apolipoprotein A-II with time in sera from senescence-accelerated mice

We evaluated changes in levels by comparing serum proteins in senescence-accelerated mouse-prone 8 (SAMP8) mice at 2, 6, 12, and 15 months of age (SAMP8-2 m, -6 m, -12 m, -15 m) to age-matched SAM-resistant 1 (SAMR1) mice. Mice were sacrificed, and blood was analyzed by 2-dimensional electrophoresis combined with mass spectrometry. Five protein spots were present in all SAMP8 serum samples, but only appeared in SAMR1 samples at 15 months of age except for spot 3, which also showed a slight expression in SAMR1-12 m sera. Two proteins decreased in the sera from SAMP8-2 m, -6 m, and -12 m mice, and divided into 2 spots each in SAMP8-15 m sera. Thus, the total number of altered spots in SAMP8 sera was 7; of these, 4 were identified as Ig kappa chain V region (M-T413), chain A of an activity suppressing Fab fragment to cytochrome P450 aromatase (32C2_A), alpha-fetoprotein, and apolipoprotein A-II. M-T413 is a monoclonal CD4 antibody, which inhibits T cell proliferation. We found that M-T413 RNA level was significantly enhanced in splenocytes from SAMP8-2 m mice. This agreed with serum M-T413 protein alterations and a strikingly lower blood CD4⁺ T cell count in SAMP8 mice when compared to the age-matched SAMR1 mice, with the latter negatively correlating with serum M-T413 protein volume. Age-related changes in serum proteins favored an increase in autoantibodies and alpha-fetoprotein and a decrease of apolipoprotein A-II, which occurred in SAMP8 mice at 2 months of age and onwards. These proteins may serve as candidate biomarkers for early aging.

Implication of JNK pathway on tau pathology and cognitive decline in a senescence-accelerated mouse model

The senescence accelerated mouse-prone 8 (SAMP8) strain of mice is an experimental model of accelerated senescence that also shares several pathological features with Alzheimer's disease. Among them, cognitive impairments and abnormal hyperphosphorylation of tau are ameliorated by the phosphodiesterase 5 inhibitor sildenafil, possibly through the modulation of Cdk5/p25 and Akt/GSK-3β pathways. Here we studied the implication of protein phosphatase 2A (PP2A) and c-Jun N-terminal kinase (JNK) in the therapeutic effects of sildenafil. Results demonstrated that there were no differences in hippocampal PP2A protein levels or activity (measured by its inactive isoform phopho-PP2A Y307) when we compared 6-month old SAMP8 mice and age-matched control, SAMR1 mice, treated with saline or sildenafil (7.5mg/kg i.p. for 4 weeks). However, this same treatment of sildenafil, that had been shown to reverse the cognitive impairment and tau hyperphosphorylation in this animal model, also reversed the increased levels of activated JNK (p-JNK) found in the hippocampus of SAMP8 mice. Moreover, the administration of the JNK inhibitor, D-JNKI-1 (0.2mg/kg i.p. for 3 weeks) also ameliorated the cognitive deficits shown by SAMP8 mice in the Morris water maze and decreased hippocampal levels of phospho-c-Jun(Ser73). When phosphorylated tau (AT8 epitope) was analyzed a significant reduction was observed in the hippocampus of D-JNKI-1 treated SAMP8 mice, providing a plausible explanation for the attenuation of cognitive decline shown by these animals. These findings suggest the involvement of the JNK pathway on tau pathology and cognitive deficits shown by 6-month old SAMP8 mice. They also point to the modulation of this kinase to be among the mechanisms responsible for the beneficial effects shown by sildenafil.

Senescence-Accelerated Mice P8: A Tool to Study Brain Aging and Alzheimer's Disease in a Mouse Model

The causes of aging remain unknown, but they are probably intimately linked to a multifactorial process that affects cell networks to varying degrees. Although a growing number of aging and Alzheimer’s disease (AD) animal models are available, a more comprehensive and physiological mouse model is required. In this context, the senescence-accelerated mouse prone 8 (SAMP8) has a number of advantages, since its rapid physiological senescence means that it has about half the normal lifespan of a rodent. In addition, according to data gathered over the last five years, some of its behavioral traits and histopathology resemble AD human dementia. SAMP8 has remarkable pathological similarities to AD and may prove to be an excellent model for acquiring more in-depth knowledge of the age-related neurodegenerative processes behind brain senescence and AD in particular. We review these facts and particularly the data on parameters related to neurodegeneration. SAMP8 also shows signs of aging in the immune, vascular, and metabolic systems, among others.

Proteomic study of neuron and astrocyte cultures from senescence-accelerated mouse SAMP8 reveals degenerative changes

Senescence-accelerated prone (SAMP) strain 8 mice suffer an earlier development of cognitive age-related pathologies and a shorter life span than conventional mice. Protein alterations in astrocytes, in addition to those in neurons, may contribute to neurodegenerative damage. We applied proteomics techniques to study cell-specific early markers of brain aging-related degeneration in SAMP8. The two-dimensional protein expression patterns of the SAMP8 neuron and astrocyte cultures were compared with those obtained from senescence-accelerated resistant mouse strain 1 cultures. Differentially expressed spots were identified by matrix-assisted laser desorption/ionization-time of flight peptide map fingerprinting and database search. Proteins belonged to cell pathways of energy metabolism, biosynthesis, cell transduction and signaling, stress response, and the maintenance of cytoskeletal functions. Most of the changes were cell type specific. However, there was a general increase in cell transduction, signaling, and stress-related proteins and a decrease in cytoskeletal proteins. In addition, neurons showed an increased expression of proteins involved in biosynthetic pathways. A number of the protein alterations have been previously reported in the brain tissue proteome of SAMP8, aged brain or Alzheimer's disease brain. Alterations in neuron and astrocyte proteoma indicated that both cell types are involved in the brain degenerative changes of SAMP8 mice. However, network analysis suggests that neuronal changes are more complex and have a greater influence.

Senescence-accelerated mouse (SAM) with special references to neurodegeneration models, SAMP8 and SAMP10 mice

The SAM strains, a group of related inbred strains consisting of senescence-prone inbred strains (SAMP) and senescence-resistant inbred strains (SAMR), have been successfully developed by selective inbreeding of the AKR/J strain of mice donated by the Jackson laboratory in 1968. The characteristic feature of aging common to the SAMP and SAMR is accelerated senescence and normal aging, respectively. Furthermore, SAMP and SAMR strains of mice manifest various pathobiological phenotypes spontaneously. Among SAMP strains, SAMP8 and SAMP10 mice show age-related behavioral deterioration such as deficits in learning and memory, emotional disorders (reduced anxiety-like behavior and depressive behavior) and altered circadian rhythm associated with certain pathological, biochemical and pharmacological changes. Here, the previous and recent literature on SAM mice are reviewed with an emphasis on SAMP8 and SAMP10 mice. A spontaneous model like SAM with distinct advantages over the gene-modified model is hoped by investigators to be used more widely as a biogerontological resource to explore the etiopathogenesis of accelerated senescence and neurodegenerative disorders.

Expression profiling in the aging brain: a perspective

To evaluate molecular events associated with the aging process in animal models and human tissues, microarray analysis is performed at the regional and cellular levels to define transcriptional patterns or mosaics that may lead to better understanding of the mechanism(s) that drive senescence. In this review, we outline the experimental and analytical issues associated with high-throughput genomic analyses in aging brain and other tissues for a comprehensive evaluation of the current state of microarray analysis in aging paradigms. Ultimately, the goal of these studies is to apply functional genomics and proteomics approaches to aging research to develop new tools to assess age in cell- and tissue-specific manners in order to develop aging biomarkers for pharmacotherapeutic interventions and disease prevention.

Effects of age and caloric restriction on brain neuronal cell death/survival

Aging may pose a challenge to the central nervous system, increasing its susceptibility to apoptotic events. Recent findings indicate that caloric restriction (CR) may have a profound effect on brain function and vulnerability to injury and diseases, by enhancing neuroprotection, stimulating the production of new neurons, and increasing synaptic plasticity. Apoptosis and apoptotic regulatory proteins in the brain frontal cortex of 6-month-old ad libitum fed (6AD), 26-month-old ad libitum fed (26AD), and 26-month-old caloric-restricted (26CR) male Fischer 344 rats (40% restriction compared to ad libitum fed) were investigated. Levels of Poly-ADP ribose polymerase (PARP-DNA repair enzyme; its cleaved 89 kDA fragment is a marker of apoptosis), cytoplasmic histone-associated DNA fragments, and X chromosome-linked inhibitor of apoptosis (XIAP--an endogenous apoptosis inhibitor) were determined. A significant age-associated increase in PARP was found, which was ameliorated in the frontal cortices of the CR rats. No significant differences in cytoplasmic histone-associated DNA fragments with age or with CR were observed. XIAP levels significantly increased with age in the brains of the ad libitum animals, while CR animals exhibited the highest levels of this inhibitor compared to all groups. Our findings suggest that caloric restriction may provide neuroprotection to the aging brain by preserving DNA repair enzymes in their intact form, and/or upregulating specific antiapoptotic proteins involved in neuronal cell death.

Age-related trends in gene expression in the chemosensory-nasal mucosae of senescence-accelerated mice

We have utilized high-density GeneChip oligonucleotide arrays to investigate the use of the senescence-accelerated mouse (SAM) as a biogerontological resource to identify patterns of gene expression in the chemosensory-nasal mucosa. Gene profiling in chronologically young and old mice of the senescence-resistant (SAMR) and senescence-prone (SAMP) strains revealed 133 known genes that were modulated by a three-fold or greater change either in one strain or the other or in both strains during aging. We also identified known genes in our study which based on their encoded proteins were identified as aging-related genes in the aging neocortex and cerebellum of mice as reported by Lee et al. (2000) [Nat. Genet. 25 (2000) 294]. Changes in gene profiles for chemosensory-related genes including olfactory and vomeronasal receptors, sensory transduction-associated proteins, and odor and pheromone transport molecules in the young SAMR and SAMP were compared with age-matched C57BL/6J mice. An analysis of known gene expression profiles suggests that changes in the expression of immune factor genes and genes associated with cell cycle progression and cell death were particularly prominent in the old SAM strains. A preliminary cellular validation study supported the dysregulation of cell cycle-related genes in the old SAM strains. The results of our initial study indicated that the use of the SAM models of aging could provide substantive information leading to a more fundamental understanding of the aging process in the chemosensory-nasal mucosa at the genomic, molecular, and cellular levels.

Accelerated aging of senescence accelerated mice R-1 demonstrated by flash visually evoked cortical potentials

To determine the physiological alterations of visual functions induced by aging, the latency of the N40 peak of the flash visual evoked cortical potentials at several stimulus frequencies were analyzed from senescence accelerated mice (SAM). The senescence prone (P-8) and senescence resistant (R-1) SAM lines were studied. In both the P-8 and ICR (the standard outbred albino laboratory mouse also called CD-1) mice, the peak latency was not significantly different at 6 and 12 months of age. In contrast, there was a prolongation of the peak latency in the R-1 line at 12 months compared to that at 6 months. We conclude that there is an acceleration of the aging process in the R-1 line for visually evoked responses. Thus, the R-1 line might be an independent line suited for the study of aging effects on visual functions.

Up-regulation of PDCD4 in senescent human diploid fibroblasts

Programmed cell death 4 (PDCD4) has a common MI domain sharing with death associated protein 5 (DAP5) and a component of eukaryotic translation initiation factor (eIF4G) complex and it might also work as a tumor suppressor. We could find that the message and product of Pdcd4 gene were up-regulated in senescent human diploid fibroblasts. In yeast two hybrid analysis, the C-terminal region of PDCD4 interacted with ribosomal protein S13 (RPS13), ribosomal protein L5 (RPL5), and TI-227H. In in vitro binding assay, RPS13, a component of 40S ribosome was stably bound to PDCD4. We also found that PDCD4 was localized to polysome fractions. We could pull out eIF4G with GST-PDCD4, but eIF4E did not interact with PDCD4. From these results, we could assume that PDCD4 might regulate the eIF4G-dependent translation through direct interactions with eIF4G and RPS13 in senescent fibroblasts.

The role of apoptosis in the normal aging brain, skeletal muscle, and heart

During aging, there is a significant loss of some postmitotic cells, for example, cardiac and skeletal myocytes. Mitochondrial damage and dysfunction with age may trigger increased apoptosis, and this may explain this increase in cell loss. However, it is still unknown if apoptosis plays an important role in normal aging. In vitro it has been shown that several mitochondrial proteins can influence apoptosis, depending on factors such as the mitochondrial membrane potential and cellular redox status. It remains possible that mitochondrial dysfunction due to chronic oxidative stress with age is a cause of apoptosis in vivo. This cell loss may be due to mitochondrial-triggered apoptosis caused by age-associated increases in oxidant production or increased activation of mitochondrial permeability transition pores. Results from our laboratory and others are reviewed that relate to apoptosis in the normal aging of the brain cortex, heart, and skeletal muscle. Particular attention is paid to the role of cytochrome c release from mitochondria and alterations in the pro- and anti-apoptotic proteins, Bax and Bcl-2, respectively. Our results demonstrate that a tissue-specific adaptation of the Bcl-2/Bax ratio occurs with age and may directly influence the release of cytochrome c.

Alzheimer's disease through the eye of a mouse. Acceptance lecture for the 2001 Gayle A. Olson and Richard D. Olson prize

There is now ample evidence that beta-amyloid proteins decrease memory. The SAMP8 mouse (P8) develops an early decline in the ability to learn and to retain new information. The studies reviewed here suggest that this is due to overproduction of beta-amyloid. Both antibodies to beta-amyloid and specific antisense to the amyloid precursor protein reverse these deficits in the P8 mouse. This antisense can cross the blood brain barrier. It is hypothesized that the overproduction of beta-amyloid leads to a decline in Delta(9) desaturase activity with an alteration in membrane fatty acids. This results in altered membrane mobility leading to a decline in neurotransmitter activity and a decreased release of acetylcholine. This decreased cholinergic activity results in a decreased ability of the P8 mouse to learn and retain new information.

Apoptosis and aging: role of the mitochondria

Apoptosis research is a rapidly developing area, but the role of apoptosis is still unclear and controversial. For example, several studies document a significant loss of cardiac and skeletal myocytes during normal aging, possibly by apoptotic mechanisms. This loss in cells may be directly mediated by mitochondrial dysfunction caused by chronic exposure to oxidants and increased activation of mitochondrial permeability transition pores. This review will discuss apoptosis in the context of normal aging of T cells, cardiac myocytes, skeletal muscle, and brain cortex. Particular attention is paid to the role of the mitochondria, because they have been implicated as a major control center regulating apoptosis. Mitochondrial oxidative stress and a decline in mitochondrial energy production in vitro often leads to activation of apoptotic pathways, but whether this occurs in vivo is unclear.

DNA microarrays in neuropsychopharmacology

Recent advances in experimental genomics, coupled with the wealth of sequence information available for a variety of organisms, have the potential to transform the way pharmacological research is performed. At present, high-density DNA microarrays allow researchers to quickly and accurately quantify gene-expression changes in a massively parallel manner. Although now well established in other biomedical fields, such as cancer and genetics research, DNA microarrays have only recently begun to make significant inroads into pharmacology. To date, the major focus in this field has been on the general application of DNA microarrays to toxicology and drug discovery and design. This review summarizes the major microarray findings of relevance to neuropsychopharmacology, as a prelude to the design and analysis of future basic and clinical microarray experiments. The ability of DNA microarrays to monitor gene expression simultaneously in a large-scale format is helping to usher in a post-genomic age, where simple constructs about the role of nature versus nurture are being replaced by a functional understanding of gene expression in living organisms.