Treatment Of Alzheimer's Disease Mice Research Articles

Modulation of the intrinsic neuronal excitability by multifunctional liposomes tailored for the treatment of Alzheimer's disease.

PurposeNanotechnologies turned out to be promising in the development of diagnostic and therapeutic approaches toward neurodegenerative disorders. However, only a very scant number of nanodevices until now proved to be effective on preclinical animal models. Although specific tests in vivo are available to assess the potential toxicity of these nanodevices on cognitive functions, those to evaluate their biosafety in vitro on neurons are still to be improved.Materials and methodsWe utilized the patch-clamp technique on primary cultures of cortical neural cells isolated from neonatal rats, aiming to evaluate their electrical properties after the incubation with liposomes (mApoE-PA-LIPs), previously proved able to cross the blood–brain barrier and to be effective on mouse models of Alzheimer’s disease (AD), both in the absence and in the presence of β-amyloid peptide oligomers.ResultsData show a high degree of biocompatibility, evaluated by lactate dehydrogenase (LDH) release and MTT assay, and the lack of cellular internalization. After the incubation with mApoE-PA-LIPs, neuronal membranes show an increase in the input resistance (from 724.14±76 MΩ in untreated population to 886.06±86 MΩ in the treated one), a reduction in the rheobase current (from 29.6±3 to 24.2±3 pA in untreated and treated, respectively), and an increase of the firing frequency, consistent with an ultimate increase in intrinsic excitability. Data obtained after co-incubation of mApoE-PA-LIPs with β-amyloid peptide oligomers suggest a retention of liposome efficacy.ConclusionThese data suggest the ability of liposomes to modulate neuronal electrical properties and are compatible with the previously demonstrated amelioration of cognitive functions induced by treatment of AD mice with liposomes. We conclude that this electrophysiological approach could represent a useful tool for nanomedicine to evaluate the effect of nanoparticles on intrinsic neuronal excitability.

PLGA nanoparticles modified with a BBB-penetrating peptide co-delivering Aβ generation inhibitor and curcumin attenuate memory deficits and neuropathology in Alzheimer's disease mice.

Alzheimer's disease (AD) is the most common form of dementia, characterized by the formation of extracellular senile plaques and neuronal loss caused by amyloid β (Aβ) aggregates in the brains of AD patients. Conventional strategies failed to treat AD in clinical trials, partly due to the poor solubility, low bioavailability and ineffectiveness of the tested drugs to cross the blood-brain barrier (BBB). Moreover, AD is a complex, multifactorial neurodegenerative disease; one-target strategies may be insufficient to prevent the processes of AD. Here, we designed novel kind of poly(lactide-co-glycolic acid) (PLGA) nanoparticles by loading with Aβ generation inhibitor S1 (PQVGHL peptide) and curcumin to target the detrimental factors in AD development and by conjugating with brain targeting peptide CRT (cyclic CRTIGPSVC peptide), an iron-mimic peptide that targets transferrin receptor (TfR), to improve BBB penetration. The average particle size of drug-loaded PLGA nanoparticles and CRT-conjugated PLGA nanoparticles were 128.6 nm and 139.8 nm, respectively. The results of Y-maze and new object recognition test demonstrated that our PLGA nanoparticles significantly improved the spatial memory and recognition in transgenic AD mice. Moreover, PLGA nanoparticles remarkably decreased the level of Aβ, reactive oxygen species (ROS), TNF-α and IL-6, and enhanced the activities of super oxide dismutase (SOD) and synapse numbers in the AD mouse brains. Compared with other PLGA nanoparticles, CRT peptide modified-PLGA nanoparticles co-delivering S1 and curcumin exhibited most beneficial effect on the treatment of AD mice, suggesting that conjugated CRT peptide, and encapsulated S1 and curcumin exerted their corresponding functions for the treatment.

A novel assay to determine acetylcholinesterase activity: The application potential for screening of drugs against Alzheimer's disease.

Acetycholinesterase (AChE) that regulates hydrolysis of acetylcholine (ACh) in the brain, is an important target for treatment of Alzheimer's disease (AD), a feature of which is ACh deficiency. However, the methods to precisely determine AChE activity are still under development. We developed a new method to exploit acetylcholine-d4 as a surrogate substrate of ACh and measure product choline-d4 via liquid chromatography-tandem mass spectrometry (LC-MS/MS). This assay detected activity of AChE present in the normal mouse brain, which is consistent with the standard Ellman assay that determines products spectrophotometrically. In AD mouse models, the result of LC-MS/MS assay showed significant higher AChE activity than that seen in control normal mice, while treatment of AD mice with an AChE inhibitor, huperzine A, led to partial decreases in AChE activity. Our results suggest that this surrogate-based LC-MS/MS method is a new, sensitive and convenient assay for the determination of AChE activity, providing a useful means for screening active compounds that target AChE.

Cystatin Peptide Prevents Alzheimer's Pathology in CRND8 AD Mice

Alzheimer's disease (AD) is the most common cause of dementia, and upwards of 25 million patients worldwide suffer from AD. The cost of AD care in the United States alone is $214 Billion and expected to reach $1.2 Trillion by 2050 as the population ages. It is thought that AD results from the accumulation of plaques and tangles in the brain leading to eventual neuronal death and cognitive decline. Amyloid‐beta 42 (Aβ42) is the main component of senile plaques. While there are current treatments to address the symptoms associated with AD and cognitive decline, there are no preventative or curative treatments to address the underlying pathophysiology. We identified a peptide capable of binding selectively to Aβ42. In the CRND8 mouse model of AD, intranasal delivery of the peptide reduced the number of Aβ42 plaques by 70–80% in the hippocampus and neocortex compared to scrambled control peptide. Using molecular modeling approaches, a second‐generation peptide was made to improve Aβ42 binding capabilities. The brains of AD mice with no treatment or scrambled peptide treatment had a large accumulation of amyloid beta aggregates and plaque in the neocortex and hippocampus. Importantly, a 4‐week treatment of AD mice with the second‐generation peptide shows a dramatic reduction in the Aβ plaque load in the hippocampus and neocortex. Preliminary behavioral studies suggest that intranasal delivery of the peptide may also improve cognitive function in the Morris Water Maze test. It is proposed that this peptide is a potential disease‐modifying therapy for AD that addresses the underlying pathophysiology.Support or Funding InformationThis work was supported by funds from NIH R21 (AG037448 ) awarded to PAS.

MiR-132/212 deficiency impairs tau metabolism and promotes pathological aggregation in vivo.

Alzheimer's disease (AD) and related tauopathies comprise a large group of neurodegenerative diseases associated with the pathological aggregation of tau protein. While much effort has focused on understanding the function of tau, little is known about the endogenous mechanisms regulating tau metabolism in vivo and how these contribute to disease. Previously, we have shown that the microRNA (miRNA) cluster miR-132/212 is downregulated in tauopathies such as AD. Here, we report that miR-132/212 deficiency in mice leads to increased tau expression, phosphorylation and aggregation. Using reporter assays and cell-based studies, we demonstrate that miR-132 directly targets tau mRNA to regulate its expression. We identified GSK-3β and PP2B as effectors of abnormal tau phosphorylation in vivo. Deletion of miR-132/212 induced tau aggregation in mice expressing endogenous or human mutant tau, an effect associated with autophagy dysfunction. Conversely, treatment of AD mice with miR-132 mimics restored in part memory function and tau metabolism. Finally, miR-132 and miR-212 levels correlated with insoluble tau and cognitive impairment in humans. These findings support a role for miR-132/212 in the regulation of tau pathology in mice and humans and provide new alternatives for therapeutic development.

Preventing Alzheimer's Pathology in a Preclinical Mouse Model

More than five million people live with Alzheimer's disease (AD) in the U.S. today and the number is rapidly rising. This disease robs its victims of dignity and places untold burden on families and on the economy. Cystatin C (CysC) is highly expressed in normal brain, but drops at the onset of AD and remains low during AD progression. Forced expression of CysC lowers Aβ brain deposition in AD mouse models. Since CysC protein can both inhibit amyloid precursor protein (APP) degradation by cathepsin B and prevent Aβ fibril formation in vitro, we synthesized the Aβ‐binding portion (CysC‐AβBP), labeled it with FITC and showed that it binds specifically to Aβ42 oligomers, that it can be efficiently delivered to the brain intranasally and that, when intranasally delivered into an AD mouse model, it binds to Aβ in the hippocampus and the neocortex. In our in vivo studies, 2.7 and 4 month old CRND8 AD mouse littermates were treated intranasally with 20 micrograms of CysC‐AβBP or scrambled CysC‐AβBP peptide, twice weekly for 3 weeks. Sagittal sections of brains from untreated and treated AD mice were stained with Aβ‐specific antibody 6E10 (Covance) and Texas Red‐conjugated secondary antibody. The brains of AD mice with no treatment or scrambled peptide treatment had a large accumulation of amyloid beta aggregates and plaque in the neocortex and hippocampus. Importantly, a 3‐week treatment of AD mice with CysC‐AβBP reduces Aβ aggregates and plaque up to 80% in the hippocampus and neocortex.

Greasing the wheels of Aβ clearance in Alzheimer's Disease: The role of lipids and apolipoprotein E

Although apolipoprotein E (apoE) is the most common genetic risk factor for Alzheimer's Disease (AD), how apoE participates in AD pathogenesis remains incompletely understood. ApoE is also the major carrier of lipids in the brain. Here, we review studies showing that the lipidation status of apoE influences the metabolism of Abeta peptides, which accumulate as amyloid deposits in the neural parenchyma and cerebrovasculature. One effect of apoE is to inhibit the transport of Abeta across the blood-brain-barrier (BBB), particularly when apoE is lipidated. A second effect is to facilitate the proteolytic degradation of Abeta by neprilysin and insulin degrading enzyme (IDE), which is enhanced when apoE is lipidated. We also describe how apoE becomes lipidated and how this impacts Abeta metabolism. Specifically, genetic loss of the cholesterol transporter ABCA1 impairs apoE lipidation and promotes amyloid deposition in AD mouse models. ABCA1 catalyses the ATP-dependent transport of cholesterol and phospholipids from the plasma membrane to lipid-free apolipoproteins including apoE. Conversely, selective overexpression of ABCA1 increases apoE lipidation in the central nervous system (CNS) and eliminates the formation of amyloid plaques in vivo. Deficiency of Liver-X-Receptors (LXRs), transcription factors that stimulate ABCA1 and apoE expression, exacerbates AD pathogenesis in vivo, whereas treatment of AD mice with synthetic LXR agonists reduces amyloid load and improves cognitive performance. These studies provide new insights into the mechanisms by which apoE affects Abeta metabolism, and offer opportunities to develop novel therapeutic approaches to reduce the leading cause of dementia in the elderly.

Fibrin deposition accelerates neurovascular damage and neuroinflammation in mouse models of Alzheimer's disease

Cerebrovascular dysfunction contributes to the pathology and progression of Alzheimer's disease (AD), but the mechanisms are not completely understood. Using transgenic mouse models of AD (TgCRND8, PDAPP, and Tg2576), we evaluated blood–brain barrier damage and the role of fibrin and fibrinolysis in the progression of amyloid-β pathology. These mouse models showed age-dependent fibrin deposition coincident with areas of blood–brain barrier permeability as demonstrated by Evans blue extravasation. Three lines of evidence suggest that fibrin contributes to the pathology. First, AD mice with only one functional plasminogen gene, and therefore with reduced fibrinolysis, have increased neurovascular damage relative to AD mice. Conversely, AD mice with only one functional fibrinogen gene have decreased blood–brain barrier damage. Second, treatment of AD mice with the plasmin inhibitor tranexamic acid aggravated pathology, whereas removal of fibrinogen from the circulation of AD mice with ancrod treatment attenuated measures of neuroinflammation and vascular pathology. Third, pretreatment with ancrod reduced the increased pathology from plasmin inhibition. These results suggest that fibrin is a mediator of inflammation and may impede the reparative process for neurovascular damage in AD. Fibrin and the mechanisms involved in its accumulation and clearance may present novel therapeutic targets in slowing the progression of AD.