A case for a non-transgenic animal model of Alzheimer's disease

Tailored Melatonin- and Donepezil-Based Hybrids Targeting Pathognomonic Changes in Alzheimer's Disease: An In Vitro and In Vivo Investigation

A plethora of pathophysiological events have been shown to play a synergistic role in neurodegeneration, revealing multiple potential targets for the pharmacological modulation of Alzheimer's disease (AD). In continuation to our previous work on new indole- and/or donepezil-based hybrids as neuroprotective agents, the present study reports on the beneficial effects of lead compounds of the series on key pathognomonic features of AD in both cellular and in vivo models. An enzyme-linked immunosorbent assay (ELISA) was used to evaluate the anti-fibrillogenic properties of 15 selected derivatives and identify quantitative changes in the formation of neurotoxic β-amyloid (Aβ42) species in human neuronal cells in response to treatment. Among the most promising compounds were 3a and 3c, which have recently shown excellent antioxidant and anticholinesterase activities, and, therefore, have been subjected to further in vivo investigation in mice. An acute toxicity study was performed after intraperitoneal (i.p.) administration of both compounds, and 1/10 of the LD50 (35 mg/kg) was selected for subacute treatment (14 days) with scopolamine in mice. Donepezil (DNPZ) and/or galantamine (GAL) were used as reference drugs, aiming to establish any pharmacological superiority of the multifaceted approach in battling hallmark features of neurodegeneration. Our promising results give first insights into emerging disease-modifying strategies to combine multiple synergistic activities in a single molecule.

Brain-targeted lycopene-loaded microemulsion modulates neuroinflammation, oxidative stress, apoptosis and synaptic plasticity in β-amyloid-induced Alzheimer's disease mice

OBJECTIVES

β-Amyloid protein (Aβ) plays pivotal roles in pathogenesis of Alzheimer's disease (AD) and triggers various pathophysiological events. Lycopene is a promising neuroprotector with multiple bioactivities, while its bioavailability is limited. Lycopene-loaded microemulsion (LME) possessing superior bioavailability and brain-targeting efficiency was developed in our previous study. In this investigation, we aimed to comprehensively evaluate its neuroprotective effects and underlying mechanisms using intracerebroventricular (ICV) Aβ_1-42 injection mice.

METHODS

Mice were assigned to the Sham, Aβ, Aβ + LME and Aβ + lycopene dissolved in olive oil (LOO) groups. ICV Aβ_1-42 administration was performed, followed by oral gavage of brain-targeted LME or conventional LOO formulation for 3 weeks. Brain samples were harvested for immunohistochemistry, biochemical assays and western blotting analyses.

RESULTS

Our findings verified Aβ-induced neurotoxicity on neuroinflammation, oxidative stress, apoptosis, Aβ metabolisms and synaptic plasticity. LME supplementation dramatically attenuated astrocytosis and microgliosis, decreased malondialdehyde production and rescued antioxidant capacities, normalized apoptotic parameters and alleviated neuronal loss, inhibited amyloidogenic processing and activated non-amyloidogenic pathway, together with upregulating synaptic protein expressions and restoring synaptic plasticity. Nevertheless, most of these phenomena were not observed for mice treated with LOO, implying that LME showed significantly higher therapeutic efficacy against Aβ injury.

DISCUSSION

In summary, brain-targeted LME could exert neuroprotective function via suppressing a series of cascades triggered by Aβ aggregates, thus ameliorating Aβ neurotoxicity and associated abnormalities. Given this, LME may serve as an attractive candidate for AD prevention and treatment, and superiority of brain-targeting delivery is highlighted.

Dual role of nitric oxide in Alzheimer's Disease

Nitric oxide (NO), an enzymatic product of nitric oxide synthase (NOS), has been associated with a variety of neurological diseases such as Alzheimer's disease (AD). NO has long been thought to contribute to neurotoxic insults caused by neuroinflammation in AD. This perception shifts as more attention is paid to the early stages before cognitive problems manifest. However, it has revealed a compensatory neuroprotective role for NO that protects synapses by increasing neuronal excitability. NO can positively affect neurons by inducing neuroplasticity, neuroprotection, and myelination, as well as having cytolytic activity to reduce inflammation. NO can also induce long-term potentiation (LTP), a process by which synaptic connections among neurons become more potent. Not to mention that such functions give rise to AD protection. Notably, it is unquestionably necessary to conduct more research to clarify NO pathways in neurodegenerative dementias because doing so could help us better understand their pathophysiology and develop more effective treatment options. All these findings bring us to the prevailing notion that NO can be used either as a therapeutic agent in patients afflicted with AD and other memory impairment disorders or as a contributor to the neurotoxic and aggressive factor in AD. In this review, after presenting a general background on AD and NO, various factors that have a pivotal role in both protecting and exacerbating AD and their correlation with NO will be elucidated. Following this, both the neuroprotective and neurotoxic effects of NO on neurons and glial cells among AD cases will be discussed in detail.

Synthetic, Cell-Derived, Brain-Derived, and Recombinant β-Amyloid: Modelling Alzheimer's Disease for Research and Drug Development

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, characterised by the accumulation of senile plaques and tau tangles, neurodegeneration, and neuroinflammation in the brain. The development of AD is a pathological cascade starting according to the amyloid hypothesis with the accumulation and aggregation of the β-amyloid peptide (Aβ), which induces hyperphosphorylation of tau and promotes the pro-inflammatory activation of microglia leading to synaptic loss and, ultimately, neuronal death. Modelling AD-related processes is important for both studying the molecular basis of the disease and the development of novel therapeutics. The replication of these processes is often achieved with the use of a purified Aβ peptide. However, Aβ preparations obtained from different sources can have strikingly different properties. This review aims to compare the structure and biological effects of Aβ oligomers and aggregates of a higher order: synthetic, recombinant, purified from cell culture, or extracted from brain tissue. The authors summarise the applicability of Aβ preparations for modelling Aβ aggregation, neurotoxicity, cytoskeleton damage, receptor toxicity in vitro and cerebral amyloidosis, synaptic plasticity disruption, and cognitive impairment in vivo and ex vivo. Further, the paper discusses the causes of the reported differences in the effect of Aβ obtained from the sources mentioned above. This review points to the importance of the source of Aβ for AD modelling and could help researchers to choose the optimal way to model the Aβ-induced abnormalities.

Oral microbiota in human systematic diseases

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment. The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling, hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases, and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.

Rab35 and glucocorticoids regulate APP and BACE1 trafficking to modulate Aβ production

Chronic stress and elevated glucocorticoids (GCs), the major stress hormones, are risk factors for Alzheimer’s disease (AD) and promote AD pathomechanisms, including overproduction of toxic amyloid-β (Aβ) peptides and intraneuronal accumulation of hyperphosphorylated Tau protein. The latter is linked to downregulation of the small GTPase Rab35, which mediates Tau degradation via the endolysosomal pathway. Whether Rab35 is also involved in Aβ overproduction remains an open question. Here, we find that hippocampal Rab35 levels are decreased not only by stress/GC but also by aging, another AD risk factor. Moreover, we show that Rab35 negatively regulates Aβ production by sorting amyloid precursor protein (APP) and β-secretase (BACE1) out of the endosomal network, where they interact to produce Aβ. Interestingly, Rab35 coordinates distinct intracellular trafficking steps for BACE1 and APP, mediated by its effectors OCRL and ACAP2, respectively. Finally, we demonstrate that Rab35 overexpression prevents the amyloidogenic trafficking of APP and BACE1 induced by high GC levels. These studies identify Rab35 as a key regulator of APP processing and suggest that its downregulation may contribute to stress-related and AD-related amyloidogenesis.

Synaptic plasticity in Alzheimer's disease and healthy aging

The strength and efficiency of synaptic connections are affected by the environment or the experience of the individual. This property, called synaptic plasticity, is directly related to memory and learning processes and has been modeled at the cellular level. These types of cellular memory and learning models include specific stimulation protocols that generate a long-term strengthening of the synapses, called long-term potentiation, or a weakening of the said long-term synapses, called long-term depression. Although, for decades, researchers have believed that the main cause of the cognitive deficit that characterizes Alzheimer's disease (AD) and aging was the loss of neurons, the hypothesis of an imbalance in the cellular and molecular mechanisms of synaptic plasticity underlying this deficit is currently widely accepted. An understanding of the molecular and cellular changes underlying the process of synaptic plasticity during the development of AD and aging will direct future studies to specific targets, resulting in the development of much more efficient and specific therapeutic strategies. In this review, we classify, discuss, and describe the main findings related to changes in the neurophysiological mechanisms of synaptic plasticity in excitatory synapses underlying AD and aging. In addition, we suggest possible mechanisms in which aging can become a high-risk factor for the development of AD and how its development could be prevented or slowed.

5-N-ethyl Carboxamidoadenosine Stimulates Adenosine-2b Receptor-Mediated Mitogen-Activated Protein Kinase Pathway to Improve Brain Mitochondrial Function in Amyloid Beta-Induced Cognitive Deficit Mice

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with loss in memory as one of the cardinal features. 5-N-ethyl carboxamidoadenosine (NECA), an agonist of adenosine-2b receptor, exerts neuroprotective activity against several experimental conditions. Further, NECA activates mitogen-activated protein kinase (MAPK) and also attenuates mitochondrial toxicity in mammalian tissues other than brain. Moreover, there is no report on the role of A2b/MAPK-mediated signaling pathway in Aβ-induced mitochondrial toxicity in the brain of the experimental animals. Therefore, the present study evaluated the neuroprotective activity of NECA with or without MAPK inhibitor against Aβ-induced cognitive deficit and mitochondrial toxicity in the experimental rodents. Further, the effect of NECA with or without MAPK inhibitor was evaluated on Aβ-induced mitochondrial toxicity in the memory-sensitive mice brain regions. Intracerebroventricular (ICV) injection of Aβ 1-42 was injected to healthy male mice through Hamilton syringe via polyethylene tube to induce AD-like behavioral manifestations. NECA attenuated Aβ-induced cognitive impairments in the rodents. In addition, NECA ameliorated Aβ-induced Aβ accumulation and cholinergic dysfunction in the selected memory-sensitive mouse HIP, PFC, and AMY. Further, NECA significantly attenuated Aβ-induced mitochondrial toxicity in terms of decrease in the mitochondrial function, integrity, and bioenergetics in the brain regions of these animals. However, MAPKI diminished the therapeutic effects of NECA on behavioral, biochemical, and molecular observations in AD-like animals. Therefore, it can be speculated that NECA exhibits neuroprotective activity perhaps through MAPK activation in AD-like rodents. Moreover, A2b-mediated MAPK activation could be a promising target in the management of AD.

Role of amyloid β protein receptors in mediating synaptic plasticity

There are few diseases in modern biomedicine that have garnered as much scientific interest and public concern as Alzheimer's disease (AD). The amyloid hypothesis has become the dominant model of AD pathogenesis; however, the details of the hypothesis are changing over time. Recently, given the increasing recognition, subtle effects of amyloid β protein (Aβ) on synaptic efficacy may be critical to AD progression. Synaptic plasticity is the important neurochemical foundation of learning and memory. Recent studies have identified that soluble Aβ oligomers combine with certain receptors to impair synaptic plasticity in AD, which advanced the amyloid hypothesis. The aim of the present review was to summarize the role of Aβ-relevant receptors in regulating synaptic plasticity and their downstream signaling cascades, which may provide novel insights into the understanding of the pathogenesis of AD and the development of therapeutic strategies to slow down the progression of AD-associated memory decline in the early stages.

Mitochondrial Ferritin Deletion Exacerbates β-Amyloid-Induced Neurotoxicity in Mice

Mitochondrial ferritin (FtMt) is a mitochondrial iron storage protein which protects mitochondria from iron-induced oxidative damage. Our previous studies indicate that FtMt attenuates β-amyloid- and 6-hydroxydopamine-induced neurotoxicity in SH-SY5Y cells. To explore the protective effects of FtMt on β-amyloid-induced memory impairment and neuronal apoptosis and the mechanisms involved, 10-month-old wild-type and Ftmt knockout mice were infused intracerebroventricularly (ICV) with Aβ_25–35 to establish an Alzheimer's disease model. Knockout of Ftmt significantly exacerbated Aβ_25–35-induced learning and memory impairment. The Bcl-2/Bax ratio in mouse hippocampi was decreased and the levels of cleaved caspase-3 and PARP were increased. The number of neuronal cells undergoing apoptosis in the hippocampus was also increased in Ftmt knockout mice. In addition, the levels of L-ferritin and FPN1 in the hippocampus were raised, and the expression of TfR1 was decreased. Increased MDA levels were also detected in Ftmt knockout mice treated with Aβ_25–35. In conclusion, this study demonstrated that the neurological impairment induced by Aβ_25–35 was exacerbated in Ftmt knockout mice and that this may relate to increased levels of oxidative stress.

Acetylcholinesterase Inhibitors for Alzheimer's Disease Treatment Ameliorate Acetaminophen-Induced Liver Injury in Mice via Central Cholinergic System Regulation

Acetaminophen (APAP) is widely used as an analgesic and antipyretic agent, but it may induce acute liver injury at high doses. Alzheimer's disease patients, while treated with acetylcholinesterase inhibitor (AChEI), may take APAP when they suffer from cold or pain. It is generally recognized that inhibiting acetylcholinesterase activity may also result in liver injury. To clarify whether AChEI could deteriorate or attenuate APAP hepatotoxicity, the effects of AChEI on APAP hepatotoxicity were investigated. Male C57BL/6J mice were administrated with the muscarinic acetylcholine receptor (mAChR) blocker atropine (Atr), or classic α7 nicotine acetylcholine receptor (α7nAChR) antagonist methyllycaconitine (MLA) 1 hour before administration of AChEIs-donepezil (4 mg/kg), rivastigmine (2 mg/kg), huperzine A (0.2 mg/kg), or neostigmine (0.15 mg/kg)-followed by APAP (300 mg/kg). Eight hours later, the mice were euthanized for histopathologic examination and biochemical assay. The results demonstrated that the tested AChEIs, excluding neostigmine, could attenuate APAP-induced liver injury, accompanied by reduced reactive oxygen species formation, adenosine triphosphate and cytochrome C loss, c-Jun N-terminal kinase 2 (JNK2) phosphorylation, and cytokines. However, Atr or MLA significantly weakened the protective effect of AChEI by affecting mitochondrial function or JNK2 phosphorylation and inflammation response. These results suggest that central mAChR and α7nAChR, which are activated by accumulated acetylcholine resulting from AChEI, were responsible for the protective effect of AChEIs on APAP-induced liver injury. This indicates that Alzheimer's patients treated with AChEI could take APAP, as AChEI is unlikely to deteriorate the hepatotoxicity of APAP.

Designer Self-Assemble Peptides Maximize the Therapeutic Benefits of Neural Stem Cell Transplantation for Alzheimer's Disease via Enhancing Neuron Differentiation and Paracrine Action

The neuropathological hallmarks of Alzheimer's disease (AD) include the presence of extracellular amyloid-β peptide (Aβ) in the form of amyloid plaques and neuronal loss. Neural stem cell (NSC) is being scrutinized as a promising cell replacement therapy for various neurodegenerative diseases. However, the unfavorable niche at the site of degenerative disease is hostile to the survival and differentiation of transplanted cells. Here, we undertook in vitro and in vivo works to examine whether a designer self-assemble peptide (DSP), which contains one functional domain Tyr-Ile-Gly-Ser-Arg (YIGSR) derived from laminin, promotes the survival and neuronal differentiation of NSC and behavioral improvement. We found that DSP could undergo spontaneous assembly into well-ordered nanofibers, and it not only facilitated the cell viability in normal culture condition, but also decreased the number of apoptotic cells induced by Aβ in vitro. NSC seeded in DSP showed much more neuronal differentiation than that seeded in self-assemble peptide (SP) or alone. In the AD model, NSC transplantation in DSP-treated AD rats demonstrated much more obvious cognitive rescue with restoration of learning/memory function compared with NSC transplantation in SP, NSC alone, or DSP alone treated ones. Interestingly, DSP enhanced the survival and neuronal differentiation of transplanted NSC. Apoptosis levels in the CA1 region and Aβ level in the hippocampus were significantly decreased in the group of NSC transplantation in DSP. Moreover, synaptic function, indicated by the expression of pre-synaptic protein synapsin-1, was restored and the secretion of anti-inflammatory and neurotrophic factors were increased, such as IL-10, brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), and insulin-like growth factor 1 (IGF-1), while the expression of pro-inflammatory factors were decreased, such as TNF-α and IL-1β. These data firstly unveiled that the biomaterial DSP can maximize the therapeutic benefits of NSC transplantation for AD through improving the survival and differentiation of transplanted stem cells and promoting the effects of neuroprotection, anti-neuroinflammatory and paracrine action. Our results may have important clinical implications for the design of future NSC-based strategies using the biomaterials for various neurodegenerative diseases including AD.

Schisandrin B Ameliorates ICV-Infused Amyloid β Induced Oxidative Stress and Neuronal Dysfunction through Inhibiting RAGE/NF-κB/MAPK and Up-Regulating HSP/Beclin Expression

Amyloid β (Aβ)-induced neurotoxicity is a major pathological mechanism of Alzheimer’s disease (AD). Our previous studies have demonstrated that schisandrin B (Sch B), an antioxidant lignan from Schisandra chinensis, could protect mouse brain against scopolamine- and cisplatin-induced neuronal dysfunction. In the present study, we examined the protective effect of Sch B against intracerebroventricular (ICV)-infused Aβ-induced neuronal dysfunction in rat cortex and explored the potential mechanism of its action. Our results showed that 26 days co-administration of Sch B significantly improved the behavioral performance of Aβ (1–40)-infused rats in step-through test. At the same time, Sch B attenuated Aβ-induced increases in oxidative and nitrosative stresses, inflammatory markers such as inducible nitric oxide syntheses, cyclooxygenase-2, interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α, and DNA damage. Several proteins such as receptor for advanced glycation end products (RAGE), nuclear factor-κB, mitogen-activated protein kinases, and apoptosis markers were over expressed in Aβ-infused rats but were significantly inhibited by Sch B treatment. Furthermore, Sch B negatively modulated the Aβ level with simultaneous up-regulation of HSP70 and beclin, autophagy markers in Aβ-infused rats. The aforementioned effects of Sch B suggest its protective role against Aβ-induced neurotoxicity through intervention in the negative cycle of RAGE-mediated Aβ accumulation during AD patho-physiology.

Chronic stress as a risk factor for Alzheimer's disease

This review aims to point out that chronic stress is able to accelerate the appearance of Alzheimer's disease (AD), proposing the former as a risk factor for the latter. Firstly, in the introduction we describe some human epidemiological studies pointing out the possibility that chronic stress could increase the incidence, or the rate of appearance of AD. Afterwards, we try to justify these epidemiological results with some experimental data. We have reviewed the experiments studying the effect of various stressors on different features in AD animal models. Moreover, we also point out the data obtained on the effect of chronic stress on some processes that are known to be involved in AD, such as inflammation and glucose metabolism. Later, we relate some of the processes known to be involved in aging and AD, such as accumulation of β-amyloid, TAU hyperphosphorylation, oxidative stress and impairement of mitochondrial function, emphasizing how they are affected by chronic stress/glucocorticoids and comparing with the description made for these processes in AD. All these data support the idea that chronic stress could be considered a risk factor for AD.

Collaboration of geldanamycin-activated P70S6K and Hsp70 against beta-amyloid-induced hippocampal apoptosis: an approach to long-term memory and learning

One of the neuropathological hallmarks of Alzheimer's disease (AD) is the accumulation of beta-amyloid peptides (Aβ) in senile plaques. Aβ-induced oxidative stress is believed to be responsible for degeneration and apoptosis of neurons and consequent cognitive and memory deficits. Here, we investigated the possible neuroprotective effect of the heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) against amyloid pathogenesis in adult male Wistar rats. GA or vehicle was injected into the lateral cerebral ventricles of rats 24 h before injection of Aβ (1-42) in CA1 area of hippocampus. The learning and memory of the rats were assessed 7 days after injection of Aβ using passive avoidance (PA) task. As potential contributing factors in Aβ-induced memory decline, we evaluated apoptotic markers and also used terminal-transferase UTP nick end labeling (TUNEL) technique to detect apoptosis in the hippocampus of Aβ-injected rats. Our behavioral data suggest that GA pretreatment can significantly suppress memory deficits in Aβ-injected rats. There was also not only a marked increase in Hsp70 level but also upregulated 70 kDa ribosomal protein S6 kinase (p70S6K) in the hippocampus of GA-treated groups with a reduction in apoptotic factors including caspase-3, poly (ADP-ribose) polymerase, Bax/Bcl-2 ratio, and TUNEL-positive cells as well. Thus, we conclude that GA exerts its protective effects against Aβ (1-42) toxicity and memory deficits, at least in part, by upregulating of Hsp70 and P70S6K.

Omega-3 fatty acid obtained from Nannochloropsis oceanica cultures grown under low urea protect against Abeta-induced neural damage

Amyloid-beta (Abeta) protein is a key factor in the pathogenesis of Alzheimer's disease (AD). Moreover, it has been reported that oxidative stress is involved in the biochemical pathway by which Abeta can lead to neuronal dysfunction. Recently, docosahexaenoic acid (DHA; C22:6) and eicosapentaenoic acid (EPA; C20:5n-3) have been reported to protect against AD. However, these omega-3 fatty acids are frequently obtained from fish oil and may contain heavy metals. In this study, we utilized Nannochloropsis oceanica to produce omega-3 fatty acid. We observed that when urea levels (nitrogen source) were lowered from 2 to 0.2 g/L in Nannochloropsis oceanica cultures, EPA production increased. Moreover, EPA in Nannochloropsis oceanica effectively promoted antioxidant activity to counter the Abeta-induced oxidative stress in Neuro-2A cells. These results indicate that Nannochloropsis oceanica may be potentially used as a therapeutic agent or as a functional food that promotes protection against AD.

Memory-Enhancing Effects of the Crude Extract of Polygala tenuifolia on Aged Mice

Learning and memory disorders arise from distinct age-associated processes, and aging animals are often used as a model of memory impairment. The root of Polygala tenuifolia has been commonly used in some Asian countries as memory enhancer and its memory improvement has been reported in various animal models. However, there is less research to verify its effect on memory functions in aged animals. Herein, the memory-enhancing effects of the crude extract of Polygala tenuifolia (EPT) on normal aged mice were assessed by Morris water maze (MWM) and step-down passive avoidance tests. In MWM tests, the impaired spatial memory of the aged mice was partly reversed by EPT (100 and 200 mg/kg; P < 0.05) as compared with the aged control mice. In step-down tests, the nonspatial memory of the aged mice was improved by EPT (100 and 200 mg/kg; P < 0.05). Additionally, EPT could increase superoxide dismutase (SOD) and catalase (CAT) activities, inhibit monoamine oxidase (MAO) and acetyl cholinesterase (AChE) activities, and decrease the levels of malondialdehyde (MDA) in the brain tissue of the aged mice. The results showed that EPT improved memory functions of the aged mice probably via its antioxidant properties and via decreasing the activities of MAO and AChE.

Role of nuclear receptor on regulation of BDNF and neuroinflammation in hippocampus of β-amyloid animal model of Alzheimer's disease

Peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists have been reported to provide neuroprotective effects against neurodegenerative diseases. The current study was carried out to investigate the effects of chronic administration of pioglitazone, a PPAR-γ agonist, on cognitive impairment in an animal model of Alzheimer's disease induced by β-amyloid. Wistar rats received intracerebroventricular (ICV) β-amyloid (βA) application (3 nmol/3 μL), and behavioral alterations (locomotor activity and memory performance) were assessed. Animals were sacrificed immediately following the last behavioral session, and their brains were removed and dissected. Mitochondrial enzymes, oxidative parameters, inflammatory mediators (TNF-α, IL-6), caspase activity, and BDNF levels were measured in the hippocampus. ICV βA-treated rats showed a memory deficit and significantly decreased BDNF level, simultaneously, increase in mitochondrial oxidative damage and inflammatory mediators in the hippocampus. Memory impairment and oxidative damage were reversed by administration of pioglitazone (15 and 30 mg/kg). Pioglitazone also significantly restored the BDNF level and attenuated the actions of inflammatory markers in ICV βA-treated rats. However, pretreatment with PPAR-γ antagonist BADGE (15 mg/kg) with higher dose of pioglitazone significantly reversed its protective action in memory impairment in βA-treated rats, which indicates the involvement of PPAR-γ receptors mediating neuroprotective action. These results demonstrate that pioglitazone offers protection against β-amyloid-induced memory dysfunction possibly due to its antioxidant, anti-inflammatory, anti-apoptotic action and neurogenesis-like effect therefore, could have a therapeutic potential in Alzheimer's disease.

Spontaneous and induced nontransgenic animal models of AD: modeling AD using combinatorial approach

Alzheimer's disease (AD), the most common neurodegenerative and dementing disorder, is characterized by extracellular amyloid deposition, intracellular neurofibrillary tangle formation, and neuronal loss. We are still behind in AD research in terms of knowledge regarding understanding its pathophysiology and designing therapeutics because of the lack of an accurate animal model for AD. A complete animal model of AD should imitate all the cognitive, behavioral, and neuropathological features of the disease. Partial models are currently in use, which only mimic specific and not all of the components of AD pathology. Currently the transgenic animals are the popular models for AD research, but different genetic backgrounds of these transgenic animals remain a major confounding factor. This review attempts to summarize the current literature on nontransgenic animal models of AD and to highlight the potential of exploiting spontaneous and induced animal models for neuropathological, neurochemical, neurobehavioral, and neuroprotective studies of AD.

Potential prevention and treatment of maifanite for Alzheimer's disease based on behavior test, oxidative stress assay, and trace element analysis in hippocampus of Aβ(₂₅₋₃₅)-induced AD rats

This study aimed to assess whether maifanite can improve the learning and memory, and antioxidant abilities of Alzheimer's disease (AD) rats. The 70 rats were divided into seven groups: [A] normal control group, [B] AD model group, [C] sham group, [D] positive control group (donepezil), [E] low-dose maifanite group, [F] middle-dose maifanite group, [G] high-dose maifanite group. For [B], [D], [E], [F], and [G] groups, Aβ(25-35) ventricle injection was carried out, then respective medicine were administered once a day for 60 consecutive days. The step-down and step-through test were used to measure learning and memory ability. The hippocampus levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) were assayed. The hippocampus contents of Al, Fe, Cu, Zn, Se, and Mn were analyzed by inductively coupled plasma-atomic emission spectrometer. Maifanite decreased the acquisition errors and the retention errors while prolonging the step-down latency, and decreased the number of electric shocks while prolonging the first latency of AD rats. Aβ(25-35) ventricle injection initiated the decrease of SOD and GSH-Px activities and the increase of MDA content, and triggered the rise of Al, Fe, and Cu levels and the decline of Mn, Zn, and Se levels. The SOD and GSH-Px activities were enhanced followed by reduced MDA level, and the levels of Mn, Zn, and Se increased accompanied by Al, Fe, and Cu decreased in the maifanite treat groups. Maifanite could improve the learning and memory, and the antioxidant abilities of AD rats. Maifanite had the potential prevention and treatment for AD.

Mitochondrial ferritin attenuates β-amyloid-induced neurotoxicity: reduction in oxidative damage through the Erk/P38 mitogen-activated protein kinase pathways

AIMS

Mitochondrial ferritin (MtFt), which was recently discovered, plays an important role in preventing neuronal damage in 6-hydroxydopamine-induced Parkinsonism by maintaining mitochondrial iron homeostasis. Disruption of iron regulation also plays a key role in the etiology of Alzheimer's disease (AD). To explore the potential neuroprotective roles of MtFt, rats and cells were treated with Aβ(25-35) to establish an AD model.

RESULTS

We report that knockdown of MtFt expression significantly enhanced Aβ(25-35)-induced neurotoxicity as shown by dysregulation of iron homeostasis, enhanced oxidative stress, and increased cell apoptosis. Opposite results were obtained when MtFt was overexpressed in SH-SY5Y cells prior to treatment with Aβ(25-35). Further, MtFt inhibited Aβ(25-35)-induced P38 mitogen-activated protein kinase and activated extracellular signal-regulated kinase (Erk) signaling.

INNOVATION

MtFt attenuated Aβ(25-35)-induced neurotoxicity and reduced oxidative damage through Erk/P38 kinase signaling.

CONCLUSION

Our results show a protective role of MtFt in AD and suggest that regulation of MtFt expression in neuronal cells may provide a new neuroprotective strategy for AD.

Chronic stress and Alzheimer's disease-like pathogenesis in a rat model: prevention by nicotine

Environmental factors including chronic stress may play a critical role in the manifestation of Alzheimer's disease (AD).This review summarizes our studies of the aggravation of the impaired cognitive ability and its cellular and molecular correlates by chronic psychosocial stress and prevention by nicotine in an Aβ rat model of AD. We utilized three approaches: learning and memory tests in the radial arm water maze, electrophysiological recordings of the cellular correlates of memory, long-term potentiation (LTP) and long-term depression (LTD), in anesthetized rats, and immunoblot analysis of synaptic plasticity- and cognition-related signaling molecules. The Aβ rat model, representing the sporadic form of established AD, was induced by continuous i.c.v. infusion of a pathogenic dose of Aβ peptides via a 14- day osmotic pump. In this AD model, chronic stress intensified cognitive deficits, accentuated the disruption of signaling molecules levels and produced greater depression of LTP than what was seen with Aβ infusion alone. Chronic treatment with nicotine was highly efficient in preventing the effects of Aβ infusion and the exacerbating impact of chronic stress. Possible mechanisms for the effect of chronic stress are discussed.

Ergothioneine protects against neuronal injury induced by β-amyloid in mice

β-Amyloid peptides (Aβ) are neurotoxic and contribute to the development of Alzheimer's disease (AD). Ergothioneine (EGT) has been shown to protect against loss of memory and learning abilities in mice. In this study, mice were orally fed EGT (0.5 or 2 mg/kg body weight) for 16 days before treatment (i.c.v) with a single dose of Aβ1-40 in the hippocampus. After resting for 12 days to restore the body weight, the mice were again fed EGT for additional 39 days. Active avoidance tests were conducted on days 37-39 (short-memory avoidance) and on days 37, 44 and 51 (long-memory avoidance). Water maze task was used to evaluate learning and memory abilities by acquisition test and retention test. In both long-memory avoidance and water maze tests, EGT significantly decreased the escape latency and increased the frequency of successful avoidance. Furthermore, EGT significantly prevented Aβ accumulation in the hippocampus and brain lipid peroxidation, restored acetylcholinesterase (AChE) activity, maintained glutathione/glutathione disulfide ratio and superoxide dismutase activity in brain tissues of Aβ1-40-teated mice. Thus, EGT can protect against Aβ-induced loss of memory and learning abilities in mice. Further studies are required to confirm the protective effects of EGT on the development or progression of AD.

In vitro and in vivo comparisons of the effects of the fruiting body and mycelium of Antrodia camphorata against amyloid β-protein-induced neurotoxicity and memory impairment

Antrodia camphorata is a particular and precious medicinal mushroom, and its fruiting body was found to provide more efficient protection from oxidative stress and inflammation than its mycelium because of its higher content of triterpenoids, total phenols, and so on. In the previous in vitro studies, the mycelium of A. camphorata is proven to provide strong neuroprotection in neuron cells and suggested to have the potential of protection against neurotoxicity of amyloid β-protein (Aβ) known as the risk factor toward Alzheimer's disease (AD) development. However, the in vivo study and the comparison study with the fruiting body have not yet been investigated. This study compared the effect of the fruiting body and mycelium of A. camphorata on alleviating the Aβ40-induced neurocytotoxicity in the in vitro Aβ-damaged neuron cell model (PC-12 cell treated with Aβ40) and memory impairment in the in vivo AD animal model induced with a continuous brain infusion of Aβ40. In the results of in vitro and in vivo studies, the fruiting body possessed stronger anti-oxidative and anti-inflammatory abilities for inhibiting neurocytotoxicity in Aβ40-treated PC-12 cells and Aβ40 accumulation in Aβ40-infused brain than mycelium. Moreover, hyperphosphorylated tau (p-tau) protein expression, known as an important AD risk factor, was suppressed by the treatment of fruiting body rather than that of mycelium in the in vitro and in vivo studies. These comparisons supported the reasons why the fruiting body resulted in a more significant improvement effect on working memory ability than mycelium in the AD rats.

Stress acts cumulatively to precipitate Alzheimer's disease-like tau pathology and cognitive deficits

Stressful life experiences are likely etiological factors in sporadic forms of Alzheimer's disease (AD). Many AD patients hypersecrete glucocorticoids (GCs), and their GC levels correlate with the rate of cognitive impairment and extent of neuronal atrophy. Severity of cognitive deficits in AD correlates strongly with levels of hyperphosphorylated forms of the cytoskeletal protein TAU, an essential mediator of the actions of amyloid β (Aβ), another molecule with a key pathogenic role in AD. Our objective was to investigate the sequential interrelationships between these various pathogenic elements, in particular with respect to the mechanisms through which stress might precipitate cognitive decline. We thus examined whether stress, through the mediation of GCs, influences TAU hyperphosphorylation, a critical and early event in the cascade of processes leading to AD pathology. Results from healthy, wild-type, middle-aged rats show that chronic stress and GC induce abnormal hyperphosphorylation of TAU in the hippocampus and prefrontal cortex (PFC), with contemporaneous impairments of hippocampus- and PFC-dependent behaviors. Exogenous GC potentiated the ability of centrally infused Aβ to induce hyperphosphorylation of TAU epitopes associated with AD and cytoplasmic accumulation of TAU, while previous exposure to stress aggravated the biochemical and behavioral effects of GC in Aβ-infused animals. Thus, lifetime stress/GC exposure may have a cumulative impact on the onset and progress of AD pathology, with TAU hyperphosphorylation serving to transduce the negative effects of stress and GC on cognition.

Amelioration of amyloid β-induced cognitive deficits by Zataria multiflora Boiss. essential oil in a rat model of Alzheimer's disease

INTRODUCTION

The limitations of current Alzheimer's disease (AD) therapeutics have prompted investigation into innovative therapeutics focused on antiinflammatory, antioxidant, and neuroprotective agents including those from medicinal plants. Numerous plants have been tested for their potential for alleviating symptoms of AD.

AIMS

Zataria multiflora Boiss. (ZM) a member of Lamiaceae family has been used in Iranian traditional medicine for its beneficial effects on mental abilities. Therefore, the effect of its essential oil was evaluated in a rat model of AD.

METHODS

Amyloid β-protein (Aβ) fragment 25-35 was injected bilaterally in the CA1 region of rats hippocampus and the effect of different doses of ZM essential oil (50, 100, or 200 μL/kg) on cognitive function was investigated in the Morris water maze. Acute toxicity of the essential oil was also studied.

RESULTS

The results showed increases in escape latency, traveled distance, heading angle, and decreases in target quadrant entries in Aβ-received groups as compared to the control group. This impairment was reversed by ZM essential oil. The results of acute toxicity testing revealed that the calculated LD50 (1264.9 μL/kg) is much higher than the therapeutic dose (100 μL/kg).

CONCLUSIONS

It seems that antioxidant, antiinflammatory, and anticholinesterase activities of ZM or its main constituents might contribute to its beneficial effects in this model. Our findings suggest that ZM may be a potentially valuable source of natural therapeutic agents for the treatment of AD. However, further investigations are necessary to establish its clinical efficacy and potential toxicity, before any recommendations concerning its use as a medication in the treatment of AD.

Study of the effect of inhibiting galanin in Alzheimer's disease induced in rats

It is recently reported that galanin plays a role in memory decline that is the primary behavioral symptom of Alzheimer's disease. The aim of the present study was to study the impact of administration of two antidiabetic drugs that might inhibit galanin, namely glibenclamide and pioglitazone, on the behavioral, and neurochemical changes in Alzheimer's disease--induced in rats by intracerebroventricular (i.c.v.) injection of beta amyloid (Abeta). The present study was conducted on 60 male Wistar rats that were divided into 6 groups: group I (control group) which received i.c.v. scrambled peptide, group II (i.c.v.-Abeta group) which received i.c.v.-Abeta, groups III and IV that received, respectively, glibenclamide and pioglitazone daily orally for 3 weeks following scrambled peptide administration as well as groups V and VI that received, respectively, glibenclamide and pioglitazone daily orally for 3 weeks following Abeta administration. i.c.v.-Abeta resulted in significant behavioral alterations suggesting Alzheimer's disease, where there was significant impairment in spatial cognition, evaluated by Morris water maze task, and in learning and memory performance, assessed using passive-avoidance learning task. i.c.v.-Abeta also resulted in significant increase in hippocampal hyperphosphorylated tau protein as well as galanin. Administration of studied antidiabetic drugs, glibenclamide and pioglitazone, resulted in significant improvement in spatial cognition and in learning and memory performance, as well as significant decrease in hippocampal hyperphosphorylated tau protein and hippocampal galanin. Our findings suggest that a pharmacologic approach to inhibit galanin in the brain, either by glibenclamide or pioglitazone might dramatically improve symptoms in Alzheimer's disease.

Search for Solutions: Animal Models of Disease

Disease researchers use animal models to study potential etiologies, pathophysiologies, and treatments. Responsive models must be predictable, emulating human conditions, and produce results that can be extrapolated and transposed. These models are often better than in vitro study or computer models, but still have limitations. Animal models can be difficult to maintain and are usually quite costly. Numerous methods are used to develop animal models including chemical exposure, genetic "knockout or knock in," or forward genetic modeling. Recently, more accurate animal models of Alzheimer's disease, osteoporosis, cancer, and mental illness have been developed. The strengths and limitations of each are discussed.

Chronic psychosocial stress exacerbates impairment of cognition and long-term potentiation in beta-amyloid rat model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a degenerative disorder that leads to progressive cognitive decline. Alzheimer's disease develops as a result of over-production and aggregation of beta-amyloid (Abeta) peptides in the brain. The reason for variation in the gravity of symptoms among AD patients is unknown and might result from patient-related factors including lifestyle. Individuals suffering from chronic stress are at an increased risk for developing AD. This study investigated the effect of chronic psychosocial stress in Abeta rat model of AD.

METHODS

Psychosocial stress was induced with a rat intruder model. The rat model of AD was induced by 14-day osmotic pump infusion of a mixture of 300 pmol/day Abeta(1-40)/Abeta(1-42). The effect of chronic stress on the severity of Abeta-induced spatial learning and memory impairment was tested by three approaches: behavioral testing in the radial arm water maze, in vivo electrophysiological recording in anesthetized rat, and immunoblot analysis to determine protein levels of learning- and memory-related molecules.

RESULTS

A marked impairment of learning and memory developed when stress was combined with Abeta, more so than that caused by Abeta alone. Additionally, there was a significantly greater impairment of early-phase long-term potentiation (E-LTP) in chronically stressed/Abeta-treated rats than in either the stressed or Abeta-treated rats. This might be a manifestation of the reduction in protein levels of calcium/calmodulin-dependent protein kinase II (CaMKII) and the abnormal increase in calcineurin levels.

CONCLUSIONS

Chronic stress significantly intensified Abeta-induced deficits of short-term memory and E-LTP by a mechanism involving decreased CaMKII activation along with increased calcineurin levels.

Effects of amyloid-β peptides on the serotoninergic 5-HT1A receptors in the rat hippocampus

A recent [(18)F]MPPF-positron emission tomography study has highlighted an overexpression of 5-HT(1A) receptors in the hippocampus of patients with mild cognitive impairment compared to a decrease in those with Alzheimer's disease (AD) [Truchot, L., Costes, S.N., Zimmer, L., Laurent, B., Le Bars, D., Thomas-Antérion, C., Croisile, B., Mercier, B., Hermier, M., Vighetto, A., Krolak-Salmon, P., 2007. Up-regulation of hippocampal serotonin metabolism in mild cognitive impairment. Neurology 69 (10), 1012-1017]. We used in vivo and in vitro neuroimaging to evaluate the longitudinal effects of injecting amyloid-β (Aβ) peptides (1-40) into the dorsal hippocampus of rats. In vivo microPET imaging showed no significant change in [(18)F]MPPF binding in the dorsal hippocampus over time, perhaps due to spatial resolution. However, in vitro autoradiography with [(18)F]MPPF (which is antagonist) displayed a transient increase in 5-HT(1A) receptor density 7 days after Aβ injection, whereas [(18)F]F15599 (a radiolabelled 5-HT(1A) agonist) binding was unchanged suggesting that the overexpressed 5-HT(1A) receptors were in a non-functional state. Complementary histology revealed a loss of glutamatergic neurons and an intense astroglial reaction at the injection site. Although a neurogenesis process cannot be excluded, we propose that Aβ injection leads to a transient astroglial overexpression of 5-HT(1A) receptors in compensation for the local neuronal loss. Exploration of the functional consequences of these serotoninergic modifications during the neurodegenerative process may have an impact on therapeutics targeting 5-HT(1A) receptors in AD.

The amyloidogenic potential and behavioral correlates of stress

Observations of elevated basal cortisol levels in Alzheimer's disease (AD) patients prompted the hypothesis that stress and glucocorticoids (GC) may contribute to the development and/or maintenance of AD. Consistent with that hypothesis, we show that stress and GC provoke misprocessing of amyloid precursor peptide in the rat hippocampus and prefrontal cortex, resulting in increased levels of the peptide C-terminal fragment 99 (C99), whose further proteolytic cleavage results in the generation of amyloid-beta (Abeta). We also show that exogenous Abeta can reproduce the effects of stress and GC on C99 production and that a history of stress strikingly potentiates the C99-inducing effects of Abeta and GC. Previous work has indicated a role for Abeta in disruption of synaptic function and cognitive behaviors, and AD patients reportedly show signs of heightened anxiety. Here, behavioral analysis revealed that like stress and GC, Abeta administration causes spatial memory deficits that are exacerbated by stress and GC; additionally, Abeta, stress and GC induced a state of hyperanxiety. Given that the intrinsic properties of C99 and Abeta include neuroendangerment and behavioral impairment, our findings suggest a causal role for stress and GC in the etiopathogenesis of AD, and demonstrate that stressful life events and GC therapy can have a cumulative impact on the course of AD development and progression.

Overview on rodent models of Alzheimer's disease

In Alzheimer's disease (AD), characteristic lesions develop in brain regions that subserve cognitive functions, ultimately leading to dementia. There are now several lesioned or transgenic small-animal models of the disease that model select aspects of cognitive deficits and/or recapitulate many, but not all, of the characteristic pathologic lesions observed in AD. This overview describes the most common approaches used to model AD in rodents, highlights their utility, and discusses some of their deficiencies.

Alzheimer disease models and human neuropathology: similarities and differences

Animal models aim to replicate the symptoms, the lesions or the cause(s) of Alzheimer disease. Numerous mouse transgenic lines have now succeeded in partially reproducing its lesions: the extracellular deposits of Abeta peptide and the intracellular accumulation of tau protein. Mutated human APP transgenes result in the deposition of Abeta peptide, similar but not identical to the Abeta peptide of human senile plaque. Amyloid angiopathy is common. Besides the deposition of Abeta, axon dystrophy and alteration of dendrites have been observed. All of the mutations cause an increase in Abeta 42 levels, except for the Arctic mutation, which alters the Abeta sequence itself. Overexpressing wild-type APP alone (as in the murine models of human trisomy 21) causes no Abeta deposition in most mouse lines. Doubly (APP x mutated PS1) transgenic mice develop the lesions earlier. Transgenic mice in which BACE1 has been knocked out or overexpressed have been produced, as well as lines with altered expression of neprilysin, the main degrading enzyme of Abeta. The APP transgenic mice have raised new questions concerning the mechanisms of neuronal loss, the accumulation of Abeta in the cell body of the neurons, inflammation and gliosis, and the dendritic alterations. They have allowed some insight to be gained into the kinetics of the changes. The connection between the symptoms, the lesions and the increase in Abeta oligomers has been found to be difficult to unravel. Neurofibrillary tangles are only found in mouse lines that overexpress mutated tau or human tau on a murine tau -/- background. A triply transgenic model (mutated APP, PS1 and tau) recapitulates the alterations seen in AD but its physiological relevance may be discussed. A number of modulators of Abeta or of tau accumulation have been tested. A transgenic model may be analyzed at three levels at least (symptoms, lesions, cause of the disease), and a reading key is proposed to summarize this analysis.

Beta-amyloid pathology in the entorhinal cortex of rats induces memory deficits: implications for Alzheimer's disease

Alzheimer's disease is characterized by the presence of senile plaques in the brain, composed mainly of aggregated amyloid-beta peptide (Abeta), which plays a central role in the pathogenesis of Alzheimer's disease and is a potential target for therapeutic intervention. Amyloid plaques occur in an increasing number of brain structures during the progression of the disease, with a heavy load in regions of the temporal cortex in the early phases. Here, we investigated the cognitive deficits specifically associated with amyloid pathology in the entorhinal cortex. The amyloid peptide Abeta(1-42) was injected bilaterally into the entorhinal cortex of rats and behavioral performance was assessed between 10 and 17 days after injection. We found that parameters of motor behavior in an open-field as well as spatial working memory tested in an alternation task were normal. In contrast, compared with naive rats or control rats injected with saline, rats injected with Abeta(1-42) showed impaired recognition memory in an object recognition task and delayed acquisition in a spatial reference memory task in a water-maze, despite improved performance with training in this task and normal spatial memory in a probe test given 24 h after training. This profile of behavioral deficits after injection of Abeta(1-42) into the entorhinal cortex was similar to that observed in another group of rats injected with the excitotoxic drug, N-methyl-d-aspartate. Immunohistochemical analysis after behavioral testing revealed that Abeta(1-42) injection induced a reactive astroglial response and plaque-like deposits in the entorhinal cortex. These results show that experimentally-induced amyloid pathology in the entorhinal cortex induces selective cognitive deficits, resembling those observed in early phases of Alzheimer's disease. Therefore, injection of protofibrillar-fibrillar Abeta(1-42) into the entorhinal cortex constitutes a promising animal model for investigating selective aspects of Alzheimer's disease and for screening drug candidates designed against Abeta pathology.

Red mold rice ameliorates impairment of memory and learning ability in intracerebroventricular amyloid β-infused rat by repressing amyloid β accumulation

Amyloid beta (Abeta) peptide related to the onset of Alzheimer's disease (AD) damaged neurons and further resulted in dementia. Monascus-fermented red mold rice (RMR), a traditional Chinese medicine as well as health food, includes monacolins (with the same function as statins) and multifunctional metabolites. In this study, ethanol extract of RMR (RE) was used to evaluate neuroprotection against Abeta40 neurotoxicity in PC12 cells. Furthermore, the effects of dietary administration of RMR on memory and learning abilities are confirmed in an animal model of AD rats infused with Abeta40 into the cerebral ventricle. During continuous Abeta40 infusion for 28 days, the rats of test groups were administered RMR or lovastatin. Memory and learning abilities were evaluated in the water maze and passive avoidance tasks. After sacrifice, cerebral cortex and hippocampus were collected for the examination of AD risk factors. The in vitro results clearly indicate that RE provides stronger neuroprotection in rescuing cell viability as well as repressing inflammatory response and oxidative stress. RMR administration potently reverses the memory deficit in the memory task. Abeta40 infusion increases acetylcholinesterase activity, reactive oxygen species, and lipid peroxidation and decreases total antioxidant status and superoxide dismutase activity in brain, but these damages were potently reversed by RMR administration, and the protection was more significant than that with lovastatin administration. The protection provided by RMR is able to prevent Abeta fibrils from being formed and deposited in hippocampus and further decrease Abeta40 accumulation, even though Abeta40 solution was infused into brain continuously.

Interactions of volatile anesthetics with neurodegenerative-disease-associated proteins

The prevalence of the neurodegenerative disorders is increasing as life expectancy lengthens, and there exists concern that environmental influences may contribute to this increase. These disorders are varied in their clinical presentation, but appear to have a common biophysical initiation. At this level, it is both plausible and now proven that anesthetics can enhance aggregation of some disease-causing proteins. Although data in support of an interaction in animal models are still lacking, data from clinical studies indicate an association, which provides further cause for concern. Many opportunities exist for rapid progress at all levels on defining whether anesthetics do indeed contribute to the pathogenesis of these progressive, debilitating disorders.