A Novel One-Day Learning Procedure for Mice

A drug cocktail of rapamycin, acarbose, and phenylbutyrate enhances resilience to features of early-stage Alzheimer's disease in aging mice

The process of aging is defined by the breakdown of critical maintenance pathways leading to an accumulation of damage and its associated phenotypes. Aging affects many systems and is considered the greatest risk factor for a number of diseases. Therefore, interventions aimed at establishing resilience to aging should delay or prevent the onset of age-related diseases. Recent studies have shown a three-drug cocktail consisting of rapamycin, acarbose, and phenylbutyrate delayed the onset of physical, cognitive, and biological aging phenotypes in old mice. To test the ability of this drug cocktail to impact Alzheimer's disease (AD), an adeno-associated-viral vector model of AD was created. Mice were fed the drug cocktail 2 months prior to injection and allowed 3 months for phenotypic development. Cognitive phenotypes were evaluated through a spatial navigation learning task. To quantify neuropathology, immunohistochemistry was performed for AD proteins and pathways of aging. Results suggested the drug cocktail was able to increase resilience to cognitive impairment, inflammation, and AD protein aggregation while enhancing autophagy and synaptic integrity, preferentially in female cohorts. In conclusion, female mice were more susceptible to the development of early stage AD neuropathology and learning impairment, and more responsive to treatment with the drug cocktail in comparison to male mice. Translationally, a model of AD where females are more susceptible would have greater value as women have a greater burden and incidence of disease compared to men. These findings validate past results and provide the rationale for further investigations into enhancing resilience to early-stage AD by enhancing resilience to aging.

Behavioral and neuropathological features of Alzheimer's disease are attenuated in 5xFAD mice treated with intranasal GHK peptide

Efforts to find disease modifying treatments for Alzheimer's disease (AD) have met with limited success in part because the focus has been on testing drugs that target a specific pathogenic mechanism. Multiple pathways have been implicated in the pathogenesis of AD. Hence, the probability of more effective treatment for AD is likely increased by using an intervention that targets more than one pathway. The naturally occurring peptide GHK (glycyl-L-histidyl-L-lysine), as a GHK-Cu complex, supports angiogenesis, remodeling, and tissue repair, has anti-inflammatory and antioxidant properties, and has been shown to improve cognitive performance in aging mice. In order to test GHK-Cu as a neurotherapeutic for AD, male and female 5xFAD transgenic mice on the C57BL/6 background at 4 months of age were given 15 mg/kg GHK-Cu intranasally 3 times per week for 3 months until 7 months of age. Results showed that intranasal GHK-Cu treatment delayed cognitive impairment, reduced amyloid plaques, and lowered inflammation levels in the frontal cortex and hippocampus. These observations suggest additional studies are warranted to investigate the potential of GHK-Cu peptide as a promising treatment for AD.

Intranasal GHK peptide enhances resilience to cognitive decline in aging mice

Brain aging and cognitive decline are aspects of growing old. Age-related cognitive impairment entails the early stages of cognitive decline, and is extremely common, affecting millions of older people. Investigation into early cognitive decline as a treatable condition is relevant to a wide range of cognitive impairment conditions, since mild age-related neuropathology increases risk for more severe neuropathology and dementia associated with Alzheimer's Disease. Recent studies suggest that the naturally occurring peptide GHK (glycyl-L-histidyl-L-lysine) in its Cu-bound form, has the potential to treat cognitive decline associated with aging. In order to test this concept, male and female C57BL/6 mice, 20 months of age, were given intranasal GHK-Cu, 15 mg/kg daily, for two months. Results showed that mice treated with intranasal GHK-Cu had an enhanced level of cognitive performance in spatial memory and learning navigation tasks, and expressed decreased neuroinflammatory and axonal damage markers compared to mice treated with intranasal saline. These observations suggest that GHK-Cu can enhance resilience to brain aging, and has translational implications for further testing in both preclinical and clinical studies using an atomizer device for intranasal delivery.

A mouse model of naturally occurring age-related cognitive impairment

Age-related cognitive impairment (ARCI) is a neurological condition that affects millions of older people, but little is known about the increased risk of developing more severe neurodegeneration and dementia. Preclinical research is needed to understand the mechanisms of the impairment and the neuropathology associated with it. We have characterized a model of naturally occurring ARCI in the C57BL/6J mouse strain that shows an age-dependent development of cognitive impairment. As in people, some mice have little cognitive impairment while others have more severe cognitive impairment. Therefore, mice can be categorized as resistant or susceptible and the two groups can be studied for behavioral and neuropathology differences. Preliminary observations show no difference in strength and agility test scores between ARCI resistant and susceptible mice of either sex suggesting the cognitive impairment in ARCI susceptible mice is not accompanied by impairment in daily living activities, similar to ARCI in humans. The hippocampal area of the brain from ARCI susceptible mice shows evidence of an increase in the inflammatory cytokine MCP-1 compared to ARCI resistant mice, suggesting inflammation may be associated with ARCI. These preliminary observations suggest that ARCI in C57BL/6J mice could be a high-impact model to study how resilience to brain aging may predict resilience to dementia associated with Alzheimer's disease and other age-related neurological conditions.

Long-term treatment with Elamipretide enhances healthy aging phenotypes in mice

Background

Disruption of metabolic and bioenergetic homeostasis related to mitochondrial dysfunction is a key driver of aging biology. Therefore, targeting mitochondrial function would be a rational approach to slowing aging. Elamipretide (Elam, a.k.a. SS-31) is a peptide known to target mitochondria and suppress mammalian signs of aging. The present study was designed to examine the phenotypic effects of long-term Elam treatment on aging in C57BL/6 mice starting at 18 months of age.

Methods

Mice were fed regular chow (RC diet) or a diet high in fat and sugar (HF diet) and treated with 3 mg/kg of Elam or saline subcutaneously 5 days per week for 10 months. Physiological performance assessments were conducted at 28 months of age.

Results

Elam improved the physical performance of males but not females, while in females Elam improved cognitive performance and enhanced the maintenance of body weight and fat mass. It also improved diastolic function in both males and females, but to a greater extent in males. The HF diet over 10 months had a negative effect on health span, as it increased body fat and decreased muscle strength and heart function, especially in females.

Conclusions

Elam enhanced healthy aging and cardiac function in both male and female mice, although the specific effects on function differed between sexes. In females, the treatment led to better cognitive performance and maintenance of body composition, while in males, performance on a rotating rod was preserved. These overall observations have translational implications for considering additional studies using Elam in therapeutic or preventive approaches for aging and age-related diseases.

Mitochondrial rRNA Methylation by Mettl15 Contributes to the Exercise and Learning Capability in Mice

Mitochondrial translation is a unique relic of the symbiotic origin of the organelle. Alterations of its components cause a number of severe human diseases. Hereby we report a study of mice devoid of Mettl15 mitochondrial 12S rRNA methyltransferase, responsible for the formation of m⁴C839 residue (human numbering). Homozygous Mettl15^−/− mice appeared to be viable in contrast to other mitochondrial rRNA methyltransferase knockouts reported earlier. The phenotype of Mettl15^−/− mice is much milder than that of other mutants of mitochondrial translation apparatus. In agreement with the results obtained earlier for cell cultures with an inactivated Mettl15 gene, we observed accumulation of the RbfA factor, normally associated with the precursor of the 28S subunit, in the 55S mitochondrial ribosome fraction of knockout mice. A lack of Mettl15 leads to a lower blood glucose level after physical exercise relative to that of the wild-type mice. Mettl15^−/− mice demonstrated suboptimal muscle performance and lower levels of Cox3 protein synthesized by mitoribosomes in the oxidative soleus muscles. Additionally, we detected decreased learning capabilities in the Mettl15^−/− knockout mice in the tests with both positive and negative reinforcement. Such properties make Mettl15^−/− knockout mice a suitable model for mild mitochondriopathies.

Short term treatment with a cocktail of rapamycin, acarbose and phenylbutyrate delays aging phenotypes in mice

Pharmaceutical intervention of aging requires targeting multiple pathways, thus there is rationale to test combinations of drugs targeting different but overlapping processes. In order to determine if combining drugs shown to extend lifespan and healthy aging in mice would have greater impact than any individual drug, a cocktail diet containing 14 ppm rapamycin, 1000 ppm acarbose, and 1000 ppm phenylbutyrate was fed to 20-month-old C57BL/6 and HET3 4-way cross mice of both sexes for three months. Mice treated with the cocktail showed a sex and strain-dependent phenotype consistent with healthy aging including decreased body fat, improved cognition, increased strength and endurance, and decreased age-related pathology compared to mice treated with individual drugs or control. The severity of age-related lesions in heart, lungs, liver, and kidney was consistently decreased in mice treated with the cocktail compared to mice treated with individual drugs or control, suggesting an interactive advantage of the three drugs. This study shows that a combination of three drugs, each previously shown to enhance lifespan and health span in mice, is able to delay aging phenotypes in middle-aged mice more effectively than any individual drug in the cocktail over a 3-month treatment period.

Neutrophil response to cyclophosphamide predicts resilience to age-related learning impairment

The ability to respond to stress, defined as resilience, was measured by white blood cell counts in C57BL/6 mice of various ages receiving a nonlethal dose of cyclophosphamide (CYP). Neutrophil counts dipped and then rebounded in a consistent and age-dependent manner. Low neutrophil rebound correlated with improved learning in middle-age mice suggesting CYP-nduced neutrophil response may predict resilience to aging.

A model for studying cutaneous wound healing and resilience to aging: Ear punch biopsy in old mice

Resilience to aging is a biological event that precedes age-related decline in physiological function and is defined as an organism's ability to respond to physical stress with increasing age. There is a need to identify factors that may predict resilience for enhancing and maintaining healthy aging. Older people often experience delayed wound healing beause of compromised tissue repair and immune response. Therefore preclincal models may be of value to investigate the relationship between cutaneous wound healing and resilience to aging. This brief report descibes an ear punch biopsy model of cutaneous wound healing in aging mice and shows that mice with biopsy ear wounds that heal more quickly have better cognition, increased strength and better running endurance later in life.

Short-term oral rapamycin prevents age-related learning impairment in mice

Effective treatments to prevent or delay age-related learning impairment are not generally available. In a preliminary preclinical study, mice 20 months of age were fed a diet containing 14 ppm rapamycin, an inhibitor of mTOR, for three months and then tested in a spatial navigation task. Mice fed the nonmedicated control diet showed learning impairment while mice fed the rapamycin diet were not learning impaired. This observation provides support for additional preclinical studies and suggests that short-term rapamycin treatment could be a possible strategy for preventing or delaying age-related cognitive impairment in people.

Adverse Neurological Effects of Short-Term Sleep Deprivation in Aging Mice Are Prevented by SS31 Peptide

Sleep deprivation is a potent stress factor that disrupts regulatory pathways in the brain resulting in cognitive dysfunction and increased risk of neurodegenerative disease with increasing age. Prevention of the adverse effects of sleep deprivation could be beneficial in older individuals by restoring healthy brain function. We report here on the ability of SS31, a mitochondrial specific peptide, to attenuate the negative neurological effects of short-term sleep deprivation in aging mice. C57BL/6 female mice, 20 months old, were subcutaneously injected with SS31 (3 mg/kg) or saline daily for four days. Sleep deprivation was 4 h daily for the last two days of SS31 treatment. Mice were immediately tested for learning ability followed by collection of brain and other tissues. In sleep deprived mice treated with SS31, learning impairment was prevented, brain mitochondrial ATP levels and synaptic plasticity regulatory proteins were restored, and reactive oxygen species (ROS) and inflammatory cytokines levels were decreased in the hippocampus. This observation suggests possible therapeutic benefits of SS31 for alleviating adverse neurological effects of short-term sleep loss.

Development of a cyclophosphamide stress test to predict resilience to aging in mice

The concept of resilience, defined as the ability to recover from stress, is a potential platform to predict healthy aging. However, specific stress tests for resilience have not yet been fully established in humans so investigations in animal models are of interest. The chemotherapeutic drug cyclophosphamide (Cyp) was selected as a chemical stressor to investigate resilience response in C57Bl/6 male mice at 4, 15, and 28 months of age. Following a single intraperitoneal injection of Cyp (100 mg/kg), tail blood was collected for counting white blood cells (WBC) every other day for 25 days, and physiological performance tests performed. Cyp induced a consistent pattern in neutrophil count in all three age groups, with a nadir at day 5 and a rebound at day 7 with different rates in each group. The neutrophil to lymphocyte ratio (NLR) showed an age-dependent rebound response 7 days after Cyp injection, with a similar pattern of decline back toward baseline. Mice in the 15-month age group with high pre-injection Cyp NLR had significantly higher total WBC counts after Cyp injection compared with mice with low pre-injection Cyp NLR, indicating a correlation between NLR and Cyp-altered WBC counts. In addition, mice with high pre-injection Cyp NLR showed significant learning impairment compared with mice with low pre-injection Cyp NLR, suggesting low NRL intensity can predict resilience to age-related cognitive decline. These observations provide the rationale to translate findings from the mouse to humans in developing in vitro Cyp stress tests.

Resilience to acute sleep deprivation is associated with attenuation of hippocampal mediated learning impairment

BACKGROUND

Sleep deprivation is a universal issue that affects individuals in different ways. While some individuals experience a deficit in performance, others experience resiliency as they maintain high levels of physical and mental activity. Sleep loss is known to cause cognitive dysfunction in areas such as learning and memory, but little is known about neural mechanisms that contribute to resilience to this adverse effect.

METHODS

An existing database of a learning paradigm in sleep deprived and non-sleep deprived 16 to 18-month old C57BL/6 mice was used to identify fast learners and slow learners based on an R2 value representing the learning curve of each individual mouse.

RESULTS

Results showed that sleep deprived mice had more slow learners compared to fast learners whereas non-sleep-deprived mice showed the opposite. Hippocampal immunohistochemistry and digital imaging analysis showed sleep deprived, fast learners expressed lower levels of monocyte chemoattractant protein-1 and histone deacetylase 2 and higher levels of synaptophysin and brain-derived neurotrophic factor compared to sleep-deprived slow learners.

CONCLUSIONS

These observations provide evidence to suggest that sleep-deprived mice that performed well in a cognitive assay show less hippocampal mediated learning impairment and provide the rationale for further investigations into neurobiological resilience to sleep deprivation with increasing age.

Sleep-deprived cognitive impairment in aging mice is alleviated by rapamycin

BACKGROUND

Sleep deprivation-induced cognitive impairment is a major health concern and an age-related risk factor for dementia. There is an urgent need to develop ways of preventing the adverse neurological effects of sleep deprivation, but current preclinical animal models of short-term sleep deprivation are not well described.

METHODS

C57BL6 mice of varying ages were sleep deprived for 4 hours a day for 4 days, and then tested with a Box maze navigation task.

RESULTS

Sleep deprived mice at young, middle and older ages showed learning impairment that varied by strain and gender. In general, females were more sensitive to sleep deprivation than males. To determine whether sleep deprivation-induced learning impairment would respond to therapeutic intervention, an independent cohort of mice was treated with rapamycin daily during the 4 days of sleep deprivation. Mice that were sleep deprived and treated with rapamycin showed significant improvement in learning time suggesting that the cognitive impairment might be associated in part with molecular and cellular mechanisms targeted by rapamycin.

CONCLUSIONS

The observations from this study suggest that aging mice would be productive models to study pathobiology and therapeutic intervention of cognitive impairment triggered by age-related sleeping disorders in people.