Background: Inflammation is associated with Aβ pathology in Alzheimer's disease (AD) and transgenic AD models. Previously, it has been demonstrated that chronic stimulation of the immune response induces pro-inflammatory cytokines IL-1β and TNF-α which contribute to neurodegeneration. However, recent evidence has shown that inducing the adaptive immune response reduces Aβ pathology and is neuroprotective. Low concentrations of IFN-γ modulate the adaptive immune response by directing microglia to differentiate to antigen presenting cells. Our objective was to determine if exercise could induce a shift from the immune profile in aged (17-19 months) Tg2576 mice to a response that reduces Aβ pathology.

Background Human studies on exercise, cognition, and apolipoprotein E (APOE) genotype show that ε4 carriers may benefit from regular physical activity. Methods We examined voluntary wheel-running, memory, and hippocampal plasticity in APOE ε3 and APOE ε4 transgenic mice at 10–12 months of age. Results Sedentary ε4 mice exhibited deficits in cognition on the radial-arm water maze (RAWM), a task dependent on the hippocampus. Six weeks of wheel-running in ε4 mice resulted in improvements on the RAWM to the level of ε3 mice. Hippocampal brain-derived neurotrophic factor (BDNF) levels were similar in ε3 and ε4 mice, and after exercise BDNF was similarly increased in both ε3 and ε4 mice. In sedentary ε4 mice, tyrosine kinase B (Trk B) receptors were reduced by 50%. Exercise restored Trk B in ε4 mice to the level of ε3 mice, and in ε4 mice, exercise dramatically increased synaptophysin, a marker of synaptic function. Conclusions Our results support the hypothesis that exercise can improve cognitive function, particularly in ε4 carriers.

Exercise is a treatment paradigm that can ameliorate cognitive dysfunction in Alzheimer disease (AD) and AD mouse models. Since exercise is also known to alter the peripheral immune response, one potential mechanism for the cognitive improvement following exercise may be by modulating the inflammatory repertoire in the central nervous system. We investigated the effects of voluntary exercise in the Tg2576 mouse model of AD at a time-point at which pathology has already developed. Inflammatory mRNA markers are increased in sedentary Tg2576 mice versus non-transgenic controls. We demonstrate that short-term voluntary wheel running improved spatial learning in aged transgenic mice as compared to sedentary Tg2576 controls. Inflammatory profiles of the Tg2576 and non-transgenic mice were different following exercise with the non-transgenic mice showing a broader response as compared to the Tg2576. Notably, exercising Tg2576 exhibited increases in a few markers including CXCL1 and CXCL12, two chemokines that may affect cognition.

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If begun early in life, exercise effectively reduces the development of cognitive deficits in transgenic mouse models of Alzheimer's disease (AD). However, the effectiveness of exercise, once the cognitive impairments are established, is not as clear. In terms of translating research in animal models to treatments involving exercise in Alzheimer's disease patients, it is critical to evaluate exercise intervention at time points that address not only prevention, but also treatment of cognitive decline. We provided exercise wheels to Tg2576 (TG) (n=12) and C57BL6 (WT) (n=17) mice at 16-18 months of age for three weeks. At this age animals have significant cognitive impairment and neuropathology consistent with AD. Age matched sedentary TG (n=13) and WT (n=12) mice were also included, as well as groups provided access to an immobile wheel (TG n=9, WT n=12). After three weeks, animals were evaluated in a radial arm water maze. Significant impairments were observed in the sedentary TG mice compared to WT in reference/long-term and working/short-term memory, as well as in probe trials. Exercised TG mice demonstrated improvements in memory, which made them indistinguishable from WT mice on all tasks. In addition, animals provided with an immobile wheel exhibited improvement in some, but not all cognitive measures. Our findings demonstrate that exercise can improve cognitive performance in a mouse model of AD even if applied after the development of pathology.

Alzheimer's disease (AD) is characterized by the accumulation of plaques containing ␤-amyloid (A␤) and neurofibrillary tangles (NFTs) consisting of modified tau. Although A␤ deposition is thought to precede the formation of NFTs in AD, the molecular steps connecting these two pathologies is not known. Previous studies have suggested that caspase activation plays an important role in promoting the pathology associated with AD. To further understand the contribution of caspases in disease progression, a triple transgenic Alzheimer's mouse model overexpressing the anti-apoptotic protein Bcl-2 was generated. Here we show that overexpression of Bcl-2 limited caspase-9 activation and reduced the caspase cleavage of tau. Moreover, overexpression of Bcl-2 attenuated the processing of APP (amyloid precursor protein) and tau and reduced the number of NFTs and extracellular deposits of A␤ associated with these animals. In addition, overexpression of Bcl-2 in 3xTg-AD mice improved place recognition memory. These findings suggest that the activation of apoptotic pathways may be an early event in AD and contributes to the pathological processes that promote the disease mechanisms underlying AD.

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Clobazam (CLB), a 1,5-benzodiazepine (BZD), was FDA-approved in October 2011 for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome (LGS) in patients 2 years and older. BZDs exert various CNS effects through allosteric modulation of GABAA receptors. The structurally distinct, 1,4-BZD clonazepam (CLN) is also approved to treat LGS. The precise mechanisms of action and clinical efficacy of both are unknown. Data show that the GABAA α1-subunit–selective compound zolpidem [ZOL] exhibits hypnotic/sedative effects. Conversely, data from knock-in mice carrying BZD binding site mutations suggest that the α2 subunit mediates anticonvulsant effects, without sedative actions. Hence, the specific pattern of interactions across the GABAA receptor complexes of BZDs might be reflected in their clinical efficacies and adverse effect profiles. In this study, GABAA-receptor binding affinities of CLB, N-desmethylclobazam (N-CLB, the major metabolite of CLB), CLN, and ZOL were characterized with native receptors from rat-brain homogenates and on cloned receptors from HEK293 cells transfected with combinations of α (α1, α2, α3, or α5), β2, and γ2 subtypes. Our results demonstrate that CLB and N-CLB have significantly greater binding affinities for α2- vs. α1-receptor complexes, a difference not observed for CLN, for which no distinction between α2 and α1 receptors was observed. Our experiments with ZOL confirmed the high preference for α1 receptors. These results provide potential clues to a new understanding of the pharmacologic modes of action of CLB and N-CLB.