Reduction In Amyloid Deposition Research Articles

Evaluation of the cerebral vascular morphostructural in a model for Alzheimer’s disease after the intervention with physical exercise.

AbstractBackgroundAlzheimer’s disease (AD) is the most common neurodegenerative disease in the world. It is characterized by impaired memory, thinking, orientation, and learning, thus affecting the quality of life of people whosuffer from it. The two pathognomonic hallmarks are the neuritic plaques and neurofibrillary tangles, however, the vascular system is also affected, aggravating the symptoms of the disease, being a possible hypothesis of the development of the disease. One of the most widely used animal models to study disease mechanisms is the 3xTg‐AD triple transgenic mouse that contains three mutations associated with familial AD (PS1M146V, APPSWE, and tauP301L). Among the non‐pharmacological treatments is physical exercise, which is a variety of planned, repetitive, and dosed physical activity, proving to be safe as part of the adjuvant treatment of the disease, however, its effect on the vascular system is unknown.MethodA total of 40 ten‐month‐old female mice, 3xTg‐AD (n = 20) and NonTg (n = 20), equally divided into exercise and sedentary groups, were used. An intervention of voluntary physical exercise was carried out for 3 months with a frequency of 5 times a week. Subsequently, memory and learning were evaluated using the Barnes maze test. The vascular morphostructure by anatomical analysis through histological assays using markers for vascular basement membrane (anti‐Collagen IV) and pericytes (anti‐PDGFR‐β), in addition to amyloid deposits. No improvement in cognitive ability was observed, however, exercise promoted the recovery of the vascular system, as well as the reduction of amyloid deposits.ResultNo improvement in cognitive ability was observed, however, exercise promoted the recovery of the vascular system, as well as the reduction of amyloid deposits.ConclusionThe intervention with voluntary physical exercise promotes stability of the vascular system as well as the reduction of amyloid deposits in the symptomatic stages of the disease.

TREM2 as an evolving therapeutic target in Alzheimer's disease.

TREM2 as an evolving therapeutic target in Alzheimer's disease.

Pharmacodynamics Assessment of Aducanumab in 5XFAD mice: A MODEL‐AD PTC Study

AbstractBackgroundThe Preclinical Testing Core (PTC) of the Model Organism Development for Evaluation of Late Onset Alzheimer’s Disease (MODEL‐AD) consortium established a rigorous preclinical drug testing strategy with go/no‐go decision points that permits unbiased assessments of therapeutic agents. As part of the pipeline validation, the chimeric murinized therapeutic antibody aducanumab (chAducanumab), was selected for evaluation in 5XFAD mice.MethodsInitial PK modeling and simulation was guided by literature and Aβ reductions from a pilot cohort of 9 month aged 5XFAD mice following 1x/week treatment of 30 mg/kg chAducanumab for 4 weeks. These pilot data were used to inform the chronic dosing regimen for the PD study which started at an age in 5XFAD mice where significant amyloid plaque accumulation was present (9 mos). PD endpoints (n=10‐12/sex/genotype/treatment) were assessed at the conclusion of chronic treatment, and included: 18‐FDG and 18F‐AV45 PET/CT, autoradiography, immunohistochemistry, AB40 and AB42 in plasma and brain fractions, and a behavioral battery. An additional cohort was enrolled for comprehensive cognitive testing using touchscreen learning and pattern separation tasks and evaluated for electroencephalography (EEG) activity using wireless telemetry.ResultsPK/PD modeling revealed slow clearance of chAducanumab following IP dosing with a T1/2 of ∼2.5 days. Therefore, the dose regimen for chronic PD studies included 0.1, 1.56, and 30 mg/kg administered 1x weekly for 12 weeks. Treatment with chAducanumab resulted in dose‐ and sex‐dependent reduction in amyloid deposition via 18F‐AV45 PET. Glucose uptake via 18F‐FDG PET similarly showed a dose dependent reversal of glycolytic loss in key brain regions. Cognitive assessments indicated no effect on learning however an improvement in pattern separation was observed with chAducanumab in females but not males. EEG analysis revealed improvements in delta, alpha, and beta oscillations with chAducanumab treatment. Multi‐omics analysis are in progress.ConclusionschAducanumab treatment in 5XFAD mice resulted in the expected reductions in brain amyloid consistent with clinical findings. Moreover, chAducanumab showed a unique glycolytic restoration profile in 5XFAD mice and improvements in some aspects of cognitive function. Together these data positively support pipeline validation of the MODEL‐AD PTC for evaluating therapeutic antibodies.

Neuronal mitochondria-targeted micelles relieving oxidative stress for delayed progression of Alzheimer's disease

Mitochondrial dysfunction is an early event of Alzheimer's disease (AD), contributes the onset and progression of AD, and may represent an effective therapeutic target for AD intervention. Since mitochondria in central neurons are more susceptible to oxidative damage than non-neuronal cells, the specific delivery of the antioxidants to the mitochondria of impaired central neurons is crucial for achieving the therapeutic effect on AD. Here, we prepare the neuronal mitochondria-targeted micelles (CT-NM) through co-decoration with neural cell adhesion molecule (NCAM) mimetic peptide C3 for brain neuron specific binding and the triphenylphosphonium (TPP) for mitochondrial targeting. CT-NM significantly increase the encapsulated resveratrol's concentration in the neuronal mitochondria compared to the micelles modified with C3 only or the resveratrol solution. The resveratrol-loaded CT-NM alleviate the oxidative stress in the neuronal cells, resulting in stabilization of the dynamic balance of mitochondrial fission and fusion. The targeted micelles restore the cognitive performance in APP/PS1 transgenic mice to the level of wild-type mice characterized by up-regulation of sirtuin 1 expression, reduction of amyloid deposition and tau hyperphosphorylation, protection of synapses and inhibition of microglia proliferation. The results demonstrate the delay of the progression of AD through reversing neuronal mitochondrial dysfunction by the targeted delivery of antioxidants.

Multigram synthesis and in vivo efficacy studies of a novel multitarget anti-Alzheimer's compound.

We describe the multigram synthesis and in vivo efficacy studies of a donepezil‒huprine hybrid that has been found to display a promising in vitro multitarget profile of interest for the treatment of Alzheimer’s disease (AD). Its synthesis features as the key step a novel multigram preparative chromatographic resolution of intermediate racemic huprine Y by chiral HPLC. Administration of this compound to transgenic CL4176 and CL2006 Caenorhabditis elegans strains expressing human Aβ42, here used as simplified animal models of AD, led to a significant protection from the toxicity induced by Aβ42. However, this protective effect was not accompanied, in CL2006 worms, by a reduction of amyloid deposits. Oral administration for 3 months to transgenic APPSL mice, a well-established animal model of AD, improved short-term memory, but did not alter brain levels of Aβ peptides nor cortical and hippocampal amyloid plaque load. Despite the clear protective and cognitive effects of AVCRI104P4, the lack of Aβ lowering effect in vivo might be related to its lower in vitro potency toward Aβ aggregation and formation as compared with its higher anticholinesterase activities. Further lead optimization in this series should thus focus on improving the anti-amyloid/anticholinesterase activity ratio.

Cannabinoid receptor 1 deficiency in a mouse model of Alzheimer's disease leads to enhanced cognitive impairment despite of a reduction in amyloid deposition

Alzheimer's disease (AD) is characterized by amyloid-β deposition in amyloid plaques, neurofibrillary tangles, inflammation, neuronal loss, and cognitive deficits. Cannabinoids display neuromodulatory and neuroprotective effects and affect memory acquisition. Here, we studied the impact of cannabinoid receptor type 1 (CB1) deficiency on the development of AD pathology by breeding amyloid precursor protein (APP) Swedish mutant mice (APP23), an AD animal model, with CB1-deficient mice. In addition to the lower body weight of APP23/CB1−/− mice, most of these mice died at an age before typical AD-associated changes become apparent. The surviving mice showed a reduced amount of APP and its fragments suggesting a regulatory influence of CB1 on APP processing, which was confirmed by modulating CB1 expression in vitro. Reduced APP levels were accompanied by a reduced plaque load and less inflammation in APP23/CB1−/− mice. Nevertheless, compared to APP23 mice with an intact CB1, APP23/CB1−/− mice showed impaired learning and memory deficits. These data argue against a direct correlation of amyloid plaque load with cognitive abilities in this AD mouse model lacking CB1. Furthermore, the findings indicate that CB1 deficiency can worsen AD-related cognitive deficits and support a potential role of CB1 as a pharmacologic target.

Attempts at suppression of amyloidogenesis in a mouse model by a variety of anti-inflammatory agents

ObjectiveThe mainstay of AA amyloidosis prevention and treatment is suppression of inflammation. In the present study we have tried to determine the efficacy of a variety of anti-inflammatory agents at suppressing AA amyloidosis in a mouse model of the disease. MethodsAA amyloidosis was induced in Swiss male mice using amyloid enhancing factor and AgNO3. Suppression of amyloid formation was studied in comparison to saline, using i.p. injections of several non-steroidal anti-inflammatory agents, TNF-α inhibitors, interferon-α, leflunomide and a variety of chemotherapeutic agents, commonly used in the treatment of inflammatory illnesses such as methotrexate, azathioprine, chlorambucil and cyclophosphamide. The degree of splenic amyloid deposition was determined using Congo red staining of smears and a 5 grade scale. ResultsThe alkylating agents, chlorambucil and cyclophosphamide, each resulted in a significant 88% reduction in amyloid deposition, yielded the most striking effect on amyloidogenesis suppression in the enhanced mouse model (p<0.0002). The non-steroidal anti-inflammatory agents tested varied widely in their ability to suppress amyloid formation in our mouse model, but only diflunisal was significantly effective, inducing a suppression of 57% (p=0.04). Other chemotherapeutic agents tested, methotrexate and azathioprine, yielded 32% and 27% suppression, which fell short of statistical significance. Surprisingly, the immunomodulatory agents etanercept, infliximab, leflunomide and interferon-α had insignificant effects on amyloid formation in this model. ConclusionOur findings suggest that alkylating agents may have a role in the prevention of amyloidogenesis. Further testing of these agents in animal models and in the clinical setting is needed.

Treatment of experimental amyloidosis with antirheumatic drugs

Background. Because at present there is no known specific effective therapy for secondary amyloidosis, the aim of this study was to determine whether antirheumatic drugs inhibit the development of experimental AA amyloidosis induced in C57BL/6 mice by casein and fibrin injections. Materials and methods. Monotherapy with sulfasalazine (SSL) and diclofenac (D) and a combined treatment with diclofenac and prednisolone (D/P) according to prophylactic and therapeutic treatment protocols were investigated. The drugs were administered through intragastric gavage 5 times a week for 5 or 4 weeks in the following doses: D – 1 mg/kg, P – 10 mg/kg, and SSL – 100 mg/kg. A histopathological examination of splenic, kidney and hepatic tissues of mice was performed. The amount of amyloid was assessed semi-quantitatively by polarizing microscopy after Congo red staining. Results. Our study indicated that no positive effect of the prophylactic treatment with D could be seen on amyloid deposition in the target organs. Prophylactic combined treatment with D/P resulted in a significant improvement of disease symptoms and markedly reduced amyloid deposits in the spleen, kidneys and liver (p &lt; 0.02–0.001). SSL therapy alone was more successful in the prophylactic treatment of experimental amyloidosis: the decrease of amyloid deposits was statistically significant in all examined organs (p &lt; 0.04–0.001), and the suppression of amyloid formation was most significant in the kidneys and liver (p &lt; 0.004–0.001). In the therapeutic treatment of experimental amyloidosis, combined treatment with D/P showed the most pronounced inhibition of amyloid formation in the internal organs (p &lt; 0.006–0.001). The suppression (by 86.7%; p &lt; 0.001) of amyloid deposits was most notable in the liver. Treatment of mice with D alone produced a significant reduction in amyloid deposition only in the liver (p &lt; 0.03) and with SSL only in the spleen (p &lt; 0.03). Conclusions. These findings suggest that D/P and SSL at relevant doses suppress amyloidogenesis, and this suppression is possibly related to the anti-inflammatory effect of antirheumatic drugs. Although these drugs cannot completely inhibit the disease in this model, a possibility remains that they may be clinically useful in rheumatic diseases associated with the formation of amyloidogenic derivatives. Keywords: mice, experimental AA amyloidosis, antirheumatic drugs

Reduced Amyloid Deposition in Mice Overexpressing RTN3 Is Adversely Affected by Preformed Dystrophic Neurites

Reticulon 3 (RTN3) was initially identified as a negative modulator of BACE1, an enzyme that cleaves amyloid precursor protein (APP) to release beta-amyloid peptide. Interestingly, RTN3 can also form aggregates after accumulation, and increased RTN3 aggregation correlates with the formation of RTN3 immunoreactive dystrophic neurites (RIDNs) in brains of Alzheimer's cases. Transgenic mice expressing RTN3 alone develop RIDNs in their hippocampus but not in their cortex. To determine the in vivo effects of RTN3 and preformed RIDNs on amyloid deposition, we crossed bitransgenic mice expressing APP and presenilin 1 (PS1) mutations with mice overexpressing RTN3. We found that amyloid deposition in cortex, the hippocampal CA3 region, and dentate gyrus was significantly reduced in triple transgenic mice compared with bitransgenic controls. However, reduction of amyloid deposition in the hippocampal CA1 region, where RIDNs predominantly formed before amyloid deposition, was less significant. Hence, preformed RTN3 aggregates in RIDNs clearly offset the negative modulation of BACE1 activity by RTN3. Furthermore, our study indicates that the increased expression of RTN3 could result in an alteration of BACE1 intracellular trafficking by retaining more BACE1 in the endoplasmic reticulum compartment where cleavage of APP by BACE1 is less favored. Our results suggest that inhibition of RTN3 aggregation is likely to be beneficial by reducing both amyloid deposition and the formation RIDNs.

O1-03-02: Analyzing the endogenous roles of GSK-3 isoforms in APP processing in GSK-3 deficient cells

Alzheimer’s BACE1. Increased expression of RTN3 in culture reduces the production of -amyloid peptide (A ). However, RTN3 can also form high-molecular-weight RTN3 aggregates upon aberrant accumulation, and the increased RTN3 aggregation correlates with the formation of RTN3 immunoreactive dystrophic neurites (RIDNs) in brains of Alzheimer’s cases. Transgenic mice expressing RTN3 develop RIDNs in their hippocampal CA1 region but not in their cerebral cortex and the other hippocampal regions. Ultrastructural analysis confirms accumulation of RTN3-containing aggregates in RIDNs. Importantly, we show that the presence of dystrophic neurites in Tg-RTN3 mice causes impairments in spatial learning and memory, as well as synaptic plasticity, implying that RIDNs potentially contribute to AD cognitive dysfunction. Methods: By taking advantage of this unique subregional phenotype, we bred RTN3 transgenic mice with transgenic mice expressing FAD mutant APP and PS1, and asked two questions: 1) whether increased expression of RTN3 could reduce A plaques in the cerebral cortex,; 2) whether the formation of hippocampal RIDNs would affect A deposition. Results: Our results demonstrated that the dystrophic -amyloid deposition in the cortical region, the hippocampal CA3 and dentate gyrus was significantly reduced in trigenic mice. However, in the hippocampal CA1 region of trigenic mice where RIDNs occurred prior to the amyloid deposition, the reduction of amyloid deposition was not evident. We also found that RTN3 altered BACE1 intracellular trafficking as a mechanism for inhibition of BACE1 activity. This study not only provides the first evidence that increased expression of RTN3 can inhibit the dystrophic -amyloid deposition in vivo but also suggests that preformed RIDNs contribute to -amyloid deposition. Conclusions: Together, our data suggests that RTN3 may have differential roles in AD pathogenesis: in negatively regulating A plaque formation and inducing neuritic dystrophy. Our results suggest that inhibition of RTN3 aggregation is likely more beneficial by reducing both amyloid deposition and RIDNs.

Tauopathy-like Abnormalities and Neurologic Deficits in Mice Immunized With Neuronal Tau Protein

A possible role of autoimmunity in Alzheimer disease pathogenesis has recently attracted increasing attention. Vaccination with amyloid-beta peptide was reported to cause marked reduction in amyloid deposition, but it also induced encephalitis. Not much is known regarding neurofibrillary tangle-related autoimmune effects. To use the main component of tangles-microtubule-associated tau protein-to test the feasibility of active induction of a neuroautoimmune disorder in mice. Prospective, randomized controlled animal study. University medical center research laboratory. Subjects Female C57BL/6 mice. Inoculation with recombinant human tau protein emulsified in complete Freund adjuvant and with pertussis toxin. Clinical, immunologic, pathologic, and behavioral evaluations were performed. Vaccination with tau protein induced histopathologic features of Alzheimer disease and tauopathies, indicated by the presence of neurofibrillary tangle-like structures, axonal damage, and gliosis. Also, mononuclear infiltrates without demyelination in the central nervous system, accompanied by neurologic deficits (such as a limp tail and limb paralysis), were observed. Anti-tau antibodies were detected in the serum of tau-immunized mice. These results provide a link between tau autoimmunity and tauopathy-like abnormalities and indicate potential dangers of using tau for immunotherapy. This experimental autoimmune tauopathy-like model is due to a pathogenic immune response against an intraneuronal antigen and is not related to myelin antigens.

Potential Role of Oral Thiazolidinedione Therapy in Preserving ??-Cell Function in Type 2 Diabetes Mellitus

Worsening glycaemic control in type 2 diabetes mellitus relates to a decline in beta-cell function, associated with impaired negative feedback regulation of insulin release. Insulin resistance, the 'traditional' cornerstone defect of type 2 diabetes, leads to an array of adverse effects on beta cells, including hypertrophy, apoptosis and those caused by lipotoxicity and glucotoxicity. In particular, increased levels of free fatty acids and their metabolites are thought to diminish both insulin synthesis and glucose-stimulated insulin secretion. Thiazolidinediones are synthetic peroxisome proliferator-activated receptor-gamma agonists that decrease insulin resistance but, as in vitro and in vivo studies suggest, may have direct beneficial effects on pancreatic beta cells. Troglitazone, for example, demonstrated improvements in insulin secretory capacity in isolated pancreatic islets from Wistar rats and a hamster beta-cell line. In vivo studies reveal thiazolidinediones promote beta-cell survival and regranulation as well as maintenance of beta-cell mass and reduction in amyloid deposition. Clinical evidence for thiazolidinediones is largely derived from comparative trials, mainly against sulfonylureas and metformin. Data at 2 years from a number of trials are now available and establish the positive effects of thiazolidinediones on glycaemic control. Empirical evidence showing decreases in fasting plasma insulin levels with pioglitazone and rosiglitazone indicate thiazolidinediones also improve insulin sensitivity. A possible effect of thiazolidinediones on normalising asynchronous insulin secretion, as assessed in a short-term placebo-controlled study, is less established. However, recent and ongoing clinical studies are focusing attention on verifying animal and other data, which support the notion that thiazolidinediones have beneficial effects on beta-cell function. These clinical studies have shown thiazolidinediones capable of preventing or delaying the development of type 2 diabetes in a high-risk population; restoring the first-phase insulin response; and improving secretory responses to oscillations in plasma glucose levels. Many of these effects appear to be independent of improvements in insulin sensitivity. Other research efforts are examining the potential cardiovascular protective effects of thiazolidinediones. Available data imply thiazolidinediones are associated with cardiovascular risk reduction, although results from large, clinical outcome trials, currently in progress, are still needed. Improved understanding of the role that declining beta-cell function has in the development of type 2 diabetes has drawn attention to the need for hypoglycaemic agents that can address this process. Emerging evidence suggests thiazolidinediones offer specific benefits for preventing or delaying the decline in beta-cell function and, thereby, a substrate for early intervention efforts aimed at lowering the worldwide burden of type 2 diabetes.

Pharmacological Profiles of Peptide Drug Candidates for the Treatment of Alzheimer's Disease

Amyloid plaques in brain, composed of aggregates of amyloid-beta peptide, play a central role in the pathogenesis of Alzheimer's disease and represent a good target for treatment. We have shown previously that a 5-amino acid beta-sheet breaker peptide (iA beta 5p), end-protected, has the ability to induce a dramatic reduction in amyloid deposition in two different transgenic Alzheimer's models (Permanne, B., Adessi, C., Saborio, G. P., Fraga, S., Frossard, M.-J., Dewachter, I., Van Dorpe, J., Banks, W. A., Van Leuven, F., and Soto, C. (2002) FASEB J. 16, 860-862). The aim of this study was to evaluate the effect of chemical modifications of the peptide bonds at the metabolite cleavage sites on the pharmacological properties of iA beta 5p derivatives. Using a rational approach, peptide analogs were designed and tested for in vitro activity and enzymatic stability. One peptide analog containing a methyl group introduced at the nitrogen atom of one amide bond showed increased stability in vitro, a 10-fold higher in vivo half-life, and good brain uptake compared with iA beta 5p while maintaining a similar activity in vitro. Our results suggest that the pharmacological profile of beta-sheet breaker peptides can be improved to produce compounds with drug-like properties that might offer a new promise in the treatment of Alzheimer's disease.

Reduction of amyloid load and cerebral damage in a transgenic mouse model of Alzheimer's disease by treatment with a beta-sheet breaker peptide.

Genetic, neuropathological, and biochemical studies have provided strong evidence for a central role of amyloid in the pathogenesis of Alzheimer's disease (AD). We have proposed previously that peptides designed as beta-sheet breakers may be useful in preventing the formation of amyloid plaques. In this study, we describe a modified beta-sheet breaker peptide with improved pharmacological properties, a high rate of penetration across the blood-brain barrier, and the ability to induce a dramatic reduction in amyloid deposition in two different transgenic AD models. In addition, we report for the first time a significant increase in neuronal survival and a decrease in brain inflammation associated with the reduction of amyloid plaques. These results demonstrate that the process of amyloid deposition is one of the causes of neurodegeneration in AD. Moreover, our findings indicate that beta-sheet breaker peptides provide a valuable tool for evaluating further the importance of amyloid in the etiology of AD and suggest that these peptides or some of their derivatives might be good candidates for AD treatment.

Intermittent use of topical dimethyl sulfoxide in macular and papular amyloidosis.

Severe and therapy-resistant pruritus is the most prominent feature of macular (MA) and lichen (LA) amyloidosis that leads to further amyloid deposition by recurrent frictional trauma to the epidermis. Of the various therapeutic modalities with variable success, the most encouraging and beneficial effect has been observed with topical dimethyl sulfoxide (DMSO) therapy. In a previous study, we achieved marked clinical improvement in nine of 10 patients in a daily treatment regimen over 6-20 weeks, but relapses occurred in the post-treatment follow-up period. The aims of this study are to investigate whether the patients would benefit from intermittent therapy and to determine the optimal application interval of DMSO to maintain the relief of symptoms. Thirteen patients with histopathologically verified cutaneous amyloidosis (five MA, two LA and six biphasic) were enrolled in the study. They were treated once daily with a 50 or 100% DMSO solution until pruritus disappeared. Then, DMSO was applied at increasing intervals until the widest effective application interval for maintenance of relief was reached. Patients were regularly followed-up by a scoring system for pruritus, papules, and pigmentation, control biopsies, photographs, blood biochemistry, and side-effects. The mean time required for the disappearance of pruritus was 4.1 weeks. Remarkable flattening of the papules was achieved after an average therapy period of 9 weeks. After a total therapy period of 6.5 months, a nearly 50% remission in pigmentation and >70% flattening of papules were achieved. The widest effective DMSO application interval was 8.6 days. The side-effects of therapy were contact urticaria, desquamation, burning sensation, and garlic-like breath odor, which were more prominent with the higher concentration of DMSO. In interval therapy, side-effects were tolerated more easily than in daily therapy. No reduction of amyloid deposits was revealed in control biopsies. Locally applied DMSO can break the vicious "pruritus-amyloid deposition-pruritus" cycle in patients with MA and LA. In addition to its daily use, interval therapy seems to maintain this effect and enables patients to tolerate side-effects more easily.