Cognitive deficit in hippocampal-dependent tasks in Werner syndrome mouse model

Electro-Acupuncture Improve the Early Pattern Separation in Alzheimer’s Disease Mice via Basal Forebrain-Hippocampus Cholinergic Neural Circuit

Objectives

To explore the effect of electro-acupuncture (EA) treatment on pattern separation and investigate the neural circuit mechanism involved in five familial mutations (5 × FAD) mice.

Methods

Five familial mutations mice were treated with EA at Baihui (DU20) and Shenting (DU24) acupoints for 30 min each, lasting for 4 weeks. Cognitive-behavioral tests were performed to evaluate the effects of EA treatment on cognitive functions. ¹H-MRS, Nissl staining, immunohistochemistry, and immunofluorescence were performed to examine the cholinergic system alteration. Thioflavin S staining and 6E10 immunofluorescence were performed to detect the amyloid-β (Aβ). Furthermore, hM4Di designer receptors exclusively activated by designer drugs (DREADDs) virus and long-term clozapine-N-oxide injection were used to inhibit the medial septal and vertical limb of the diagonal band and dentate gyrus (MS/VDB-DG) cholinergic neural circuit. Cognitive-behavioral tests and immunofluorescence were performed to investigate the cholinergic neural circuit mechanism of EA treatment improving cognition in 5 × FAD mice.

Results

Electro-acupuncture treatment significantly improved spatial recognition memory and pattern separation impairment, regulated cholinergic system via reduction neuron loss, upregulation of choline/creatine, choline acetyltransferase, vesicular acetylcholine transporter, and downregulation of enzyme acetylcholinesterase in 5 × FAD mice. Aβ deposition was reduced after EA treatment. Subsequently, the monosynaptic hM4Di DREADDs virus tracing and inhibiting strategy showed that EA treatment activates the MS/VDB-DG cholinergic neural circuit to improve the early pattern separation. In addition, EA treatment activates this circuit to upregulating M1 receptors positive cells and promoting hippocampal neurogenesis in the dentate gyrus (DG).

Conclusion

Electro-acupuncture could improve the early pattern separation impairment by activating the MS/VDB-DG cholinergic neural circuit in 5 × FAD mice, which was related to the regulation of the cholinergic system and the promotion of neurogenesis by EA treatment.

Verapamil Prevents Development of Cognitive Impairment in an Aged Mouse Model of Sporadic Alzheimer's Disease

Currently, dementia is the only leading cause of death that is still on the rise, with total costs already exceeding those of cancer and heart disease and projected to increase even further in the coming years. Unfortunately, there are no satisfactory treatments and attempts to develop novel, more effective treatments have been extremely costly, albeit unsuccessful thus far. This has led us to investigate the use of established drugs, licensed for other therapeutic indications, for their potential application in cognitive disorders. This strategy, referred to as "drug repositioning," has been successful in many other areas including cancer and cardiovascular diseases. To our knowledge, this is the first study to investigate the effects of long-term treatment with verapamil, a calcium channel blocker commonly prescribed for various cardiovascular conditions and recently applied for prevention of cluster headaches, on the development of cognitive impairment in aged animals. Verapamil was studied at a low dose (1mg/kg/d) in a mouse model of sporadic Alzheimer's disease (sAD). Oral treatment with verapamil or vehicle was started, 24 h post-intracerebroventricular (ICV) streptozotocin/(STZ), in 12-month-old animals and continued for 3 months. Cognitive function was assessed using established tests for spatial learning, short-term/working memory, and long-term/reference memory. Our findings demonstrate that long-term low-dose verapamil effectively prevents development of ICV/STZ-induced cognitive impairment. It mitigates the astrogliosis and synaptic toxicity otherwise induced by ICV/STZ in the hippocampus of aged animals. These findings indicate that long-term, low-dose verapamil may delay progression of sAD in susceptible subjects of advanced age.

The aging brain: impact of heavy metal neurotoxicity

The aging process is accompanied by critical changes in cellular and molecular functions, which upset the homeostatic balance in the central nervous system. Accumulation of metals renders the brain susceptible to neurotoxic insults by mechanisms such as mitochondrial dysfunction, neuronal calcium-ion dyshomeostasis, buildup of damaged molecules, compromised DNA repair, reduction in neurogenesis, and impaired energy metabolism. These hallmarks have been identified to be responsible for neuronal injuries, resulting in several neurological disorders. Various studies have shown solid associations between metal accumulation, abnormal protein expressions, and pathogenesis of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and Amyotrophic lateral sclerosis. This review highlights metals (such as manganese, zinc, iron, copper, and nickel) for their accumulation, and consequences in the development of neurological disorders, in relation to the aging brain.

Nonfunctional mutant Wrn protein leads to neurological deficits, neuronal stress, microglial alteration, and immune imbalance in a mouse model of Werner syndrome

Werner syndrome (WS) is a premature aging disorder caused by mutations in a RecQ-family DNA helicase, WRN. Mice lacking part of the helicase domain of the WRN orthologue exhibit many phenotypic features of WS, including metabolic abnormalities and a shorter lifespan. Yet, little is known about the impact of WRN mutations on the central nervous system in both humans and mouse models of WS. In the current study, we have performed a longitudinal behavioral assessment on mice bearing a Wrn helicase deletion. Behavioral tests demonstrated a loss of motor activity and coordination, reduction in perception, increase in repetitive behavior, and deficits in both spatial and social novelty memories in Wrn mutant mice compared to age-matched wild type mice. These neurological deficits were associated with biochemical and histological changes in the brain of aged Wrn mutant mice. Microglia, resident immune cells that regulate neuronal plasticity and function in the brain, were hyper-ramified in multiple regions involved with the behavioral deficits of Wrn mutant mice. Furthermore, western analyses indicated that Wrn mutant mice exhibited an increase of oxidative stress markers in the prefrontal cortex. Supporting these findings, electron microscopy studies revealed increased cellular aging and oxidative stress features, among microglia and neurons respectively, in the prefrontal cortex of aged Wrn mutant mice. In addition, multiplex immunoassay of serum identified significant changes in the expression levels of several pro- and anti-inflammatory cytokines. Taken together, these findings indicate that microglial dysfunction and neuronal oxidative stress, associated with peripheral immune system alterations, might be important driving forces leading to abnormal neurological symptoms in WS thus suggesting potential therapeutic targets for interventions.

Hallmarks of Brain Aging: Adaptive and Pathological Modification by Metabolic States

During aging, the cellular milieu of the brain exhibits tell-tale signs of compromised bioenergetics, impaired adaptive neuroplasticity and resilience, aberrant neuronal network activity, dysregulation of neuronal Ca2+ homeostasis, the accrual of oxidatively modified molecules and organelles, and inflammation. These alterations render the aging brain vulnerable to Alzheimer's and Parkinson's diseases and stroke. Emerging findings are revealing mechanisms by which sedentary overindulgent lifestyles accelerate brain aging, whereas lifestyles that include intermittent bioenergetic challenges (exercise, fasting, and intellectual challenges) foster healthy brain aging. Here we provide an overview of the cellular and molecular biology of brain aging, how those processes interface with disease-specific neurodegenerative pathways, and how metabolic states influence brain health.

Role of angiotensin system modulation on progression of cognitive impairment and brain MRI changes in aged hypertensive animals - A randomized double- blind pre-clinical study

Growing evidence suggests that renin angiotensin system (RAS) modulators support cognitive function in various animal models. However, little is known about their long-term effects on the brain structure in aged hypertensive animals with chronic cerebral hypoperfusion as well as which specific domains of cognition are most affected. Therefore, in the current study we examined the effects of Candesartan and Compound 21 (C21) (RAS modulators) on aspects of cognition known to diminish with advanced age and accelerate with hypertension and vascular disease. Outcome measures for sensorimotor and cognitive function were performed using a sequence of tests, all blindly conducted and assessed at baseline and after 4 and 8 weeks of chronic hypoxic hypoperfusion and treatment. Magnetic resonance imaging (MRI) was performed at the end of the 8 week study period followed by animal sacrifice and tissue collection. Both Candesartan and C21 effectively preserved cognitive function and prevented progression of vascular cognitive impairment (VCI) but only candesartan prevented loss of brain volume in aged hypertensive animals. Collectively, our findings demonstrate that delayed administration of RAS modulators effectively preserve cognitive function and prevent the development / progression of VCI in aged hypertensive animals with chronic cerebral hypoperfusion.