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1.
Neurobiol Dis ; 198: 106526, 2024 May 09.
Article in English | MEDLINE | ID: mdl-38734152

ABSTRACT

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease with a complex origin, thought to involve a combination of genetic, biological and environmental factors. Insulin dysfunction has emerged as a potential factor contributing to AD pathogenesis, particularly in individuals with diabetes, and among those with insulin deficiency or undergoing insulin therapy. The intraperitoneal administration of streptozotocin (STZ) is widely used in rodent models to explore the impact of insulin deficiency on AD pathology, although prior research predominantly focused on young animals, with no comparative analysis across different age groups. Our study aimed to fill this gap by analyzing the impact of insulin dysfunction in 7 and 23 months 3xTg-AD mice, that exhibit both amyloid and tau pathologies. Our objective was to elucidate the age-specific consequences of insulin deficiency on AD pathology. STZ administration led to insulin deficiency in the younger mice, resulting in an increase in cortical amyloid-ß (Aß) and tau aggregation, while tau phosphorylation was not significantly affected. Conversely, older mice displayed an unexpected resilience to the peripheral metabolic impact of STZ, while exhibiting an increase in both tau phosphorylation and aggregation without significantly affecting amyloid pathology. These changes were paralleled with alterations in signaling pathways involving tau kinases and phosphatases. Several markers of blood-brain barrier (BBB) integrity declined with age in 3xTg-AD mice, which might have facilitated a direct neurotoxic effect of STZ in older mice. Overall, our research confirms the influence of insulin signaling dysfunction on AD pathology, but also advises careful interpretation of data related to STZ-induced effects in older animals.

2.
Res Sq ; 2024 May 14.
Article in English | MEDLINE | ID: mdl-38798432

ABSTRACT

The sleep-wake cycle regulates interstitial fluid and cerebrospinal fluid (CSF) tau levels in both mouse and human by mechanisms that remain unestablished. Here, we reveal a novel pathway by which wakefulness increases extracellular tau levels in mouse and humans. In mice, higher body temperature (BT) associated with wakefulness and sleep deprivation increased CSF tau. In vitro, wakefulness temperatures upregulated tau secretion via a temperature-dependent increase in activity and expression of unconventional protein secretion pathway-1 components, namely caspase-3-mediated C-terminal cleavage of tau (TauC3), and membrane expression of PIP2 and syndecan-3. In humans, the increase in both CSF and plasma tau levels observed post-wakefulness correlated with BT increase during wakefulness. Our findings suggest sleep-wake variation in BT may contribute to regulating extracellular tau levels, highlighting the importance of thermoregulation in pathways linking sleep disturbance to neurodegeneration, and the potential for thermal intervention to prevent or delay tau-mediated neurodegeneration.

3.
Methods Mol Biol ; 2754: 309-321, 2024.
Article in English | MEDLINE | ID: mdl-38512673

ABSTRACT

Tau is a microtubule-associated protein enriched in the axonal compartment. Its most well-known function is to bind and stabilize microtubules. In Alzheimer's disease and other neurodegenerative diseases known as tauopathies, tau undergoes several abnormal post-translational modifications including hyperphosphorylation, conformational changes, oligomerization, and aggregation. Numerous mouse models of tauopathies have been developed, and Western blotting remains an invaluable tool in studying tau protein physiological and pathological changes in these models. However, many of the antibodies that have been developed to analyze tau post-translational modifications are mouse monoclonal, which are at risk of producing artifactual signals in Western blotting procedures. This risk does not arise due to their lack of specificity, but rather because the secondary antibodies used to detect them will also react with the heavy chain of endogenous mouse immunoglobulins (Igs), leading to a non-specific signal at the same molecular weight as tau protein (around 50 kDa). Here, we present the use of anti-light-chain secondary antibodies as a simple and efficient technique to prevent non-specific Ig signals around 50 kDa. We demonstrate the efficacy of this method by either eliminating or identifying artifactual signals when using monoclonal antibodies directed at non-phosphorylated epitopes (T49, Tau3R, Tau4R), phosphorylated epitopes (MC6, AT180, CP13), or an abnormal tau conformation (MC1), in wild-type (WT) mice with tau hyperphosphorylation (hypothermic), transgenic mice overexpressing human tau (hTau mice), and tau knockout (TKO) mice.


Subject(s)
Alzheimer Disease , Tauopathies , Mice , Animals , Humans , tau Proteins/metabolism , Artifacts , Phosphorylation , Tauopathies/metabolism , Alzheimer Disease/metabolism , Mice, Transgenic , Mice, Knockout , Epitopes/metabolism , Brain/metabolism , Blotting, Western
4.
Methods Mol Biol ; 2754: 323-341, 2024.
Article in English | MEDLINE | ID: mdl-38512674

ABSTRACT

The intracellular accumulation of microtubule-associated protein tau is a characteristic feature of tauopathies, a group of neurodegenerative diseases including Alzheimer's disease. Formation of insoluble tau aggregates is initiated by the abnormal hyperphosphorylation and oligomerization of tau. Over the past decades, multiple transgenic rodent models mimicking tauopathies have been develop, showcasing this neuropathological hallmark. The biochemical analysis of insoluble tau in these models has served as a valuable tool to understand the progression of tau-related pathology. In this chapter, we provide a comprehensive review of the two primary methods for isolating insoluble tau, namely, sarkosyl and formic acid extraction (and their variants), which are employed for biochemical analysis in transgenic mouse models of tauopathy. We also analyze the strengths and limitations of these methods.


Subject(s)
Alzheimer Disease , Tauopathies , Mice , Animals , Rodentia/metabolism , Disease Models, Animal , Tauopathies/metabolism , tau Proteins/genetics , tau Proteins/metabolism , Alzheimer Disease/metabolism , Mice, Transgenic , Brain/metabolism
5.
J Med Chem ; 66(21): 14928-14947, 2023 11 09.
Article in English | MEDLINE | ID: mdl-37797083

ABSTRACT

The multifactorial origin and neurochemistry of Alzheimer's disease (AD) call for the development of multitarget treatment strategies. We report a first-in-class triple acting compound that targets serotonin type 6 and 3 receptors (5-HT-Rs) and monoamine oxidase type B (MAO-B) as an approach for treating AD. The key structural features required for MAO-B inhibition and 5-HT6R antagonism and interaction with 5-HT3R were determined using molecular dynamic simulations and cryo-electron microscopy, respectively. Bioavailable PZ-1922 reversed scopolamine-induced cognitive deficits in the novel object recognition test. Furthermore, it displayed superior pro-cognitive properties compared to intepirdine (a 5-HT6R antagonist) in the AD model, which involved intracerebroventricular injection of an oligomeric solution of amyloid-ß peptide (oAß) in the T-maze test in rats. PZ-1922, but not intepirdine, restored levels of biomarkers characteristic of the debilitating effects of oAß. These data support the potential of a multitarget approach involving the joint modulation of 5-HT6R/5-HT3R/MAO-B in AD.


Subject(s)
Alzheimer Disease , Serotonin , Rats , Animals , Serotonin/adverse effects , Cryoelectron Microscopy , Receptors, Serotonin , Serotonin Antagonists/pharmacology , Serotonin Antagonists/therapeutic use , Alzheimer Disease/drug therapy , Alzheimer Disease/chemically induced , Monoamine Oxidase , Cognition , Monoamine Oxidase Inhibitors/pharmacology , Monoamine Oxidase Inhibitors/therapeutic use
6.
Pharmacol Ther ; 245: 108398, 2023 05.
Article in English | MEDLINE | ID: mdl-37001735

ABSTRACT

Alzheimer's disease (AD) is the most common form of dementia in the elderly, currently affecting more than 40 million people worldwide. The two main histopathological hallmarks of AD were identified in the 1980s: senile plaques (composed of aggregated amyloid-ß (Aß) peptides) and neurofibrillary tangles (composed of hyperphosphorylated tau protein). In the human brain, both Aß and tau show aggregation into soluble and insoluble oligomers. Soluble oligomers of Aß include their most predominant forms - Aß1-40 and Aß1-42 - as well as shorter peptides such as Aß25-35 or Aß25-35/40. Most animal models of AD have been developed using transgenesis, based on identified human mutations. However, these familial forms of AD represent less than 1% of AD cases. In this context, the idea emerged in the 1990s to directly inject the Aß25-35 fragment into the rodent brain to develop an acute model of AD that could mimic the disease's sporadic forms (99% of all cases). This review aims to: (1) summarize the biological activity of Aß25-35, focusing on its impact on the main structural and functional alterations observed in AD (cognitive deficits, APP misprocessing, tau system dysfunction, neuroinflammation, oxidative stress, cholinergic and glutamatergic alterations, HPA axis dysregulation, synaptic deficits and cell death); and (2) confirm the interest of this pathomimetic model in AD research, as it has helped identify and characterize many molecules (marketed, in clinical development, and in preclinical testing), and to the development of alternative approaches for AD prevention and therapy. Today, the Aß25-35 model appears as a first-intent choice model to rapidly screen the symptomatic or neuroprotective potencies of new compounds, chemical series, or innovative therapeutic strategies.


Subject(s)
Alzheimer Disease , Animals , Humans , Aged , Alzheimer Disease/genetics , Hypothalamo-Hypophyseal System , Pituitary-Adrenal System/metabolism , Pituitary-Adrenal System/pathology , Amyloid beta-Peptides/metabolism , tau Proteins/metabolism , Oxidative Stress
7.
Exp Neurobiol ; 32(6): 423-440, 2023 Dec 31.
Article in English | MEDLINE | ID: mdl-38196137

ABSTRACT

In preclinical research on Alzheimer's disease and related tauopathies, tau phosphorylation analysis is routinely employed in both cellular and animal models. However, recognizing the sensitivity of tau phosphorylation to various extrinsic factors, notably temperature, is vital for experimental accuracy. Hypothermia can trigger tau hyperphosphorylation, while hyperthermia leads to its dephosphorylation. Nevertheless, the rapidity of tau phosphorylation in response to unintentional temperature variations remains unknown. In cell cultures, the most significant temperature change occurs when the cells are removed from the incubator before harvesting, and in animal models, during anesthesia prior to euthanasia. In this study, we investigate the kinetics of tau phosphorylation in N2a and SH-SY5Y neuronal cell lines, as well as in mice exposed to anesthesia. We observed changes in tau phosphorylation within the few seconds upon transferring cell cultures from their 37°C incubator to room temperature conditions. However, cells placed directly on ice post-incubation exhibited negligible phosphorylation changes. In vivo, isoflurane anesthesia rapidly resulted in tau hyperphosphorylation within the few seconds needed to lose the pedal withdrawal reflex in mice. These findings emphasize the critical importance of preventing temperature variation in researches focused on tau. To ensure accurate results, we recommend avoiding anesthesia before euthanasia and promptly placing cells on ice after removal from the incubator. By controlling temperature fluctuations, the reliability and validity of tau phosphorylation studies can be significantly enhanced.

8.
Antioxidants (Basel) ; 11(5)2022 Apr 25.
Article in English | MEDLINE | ID: mdl-35624701

ABSTRACT

Polyunsaturated fatty acids (PUFAs) are a class of fatty acids that are closely associated with the development and function of the brain. The most abundant PUFA is docosahexaenoic acid (DHA, 22:6 n-3). In humans, low plasmatic concentrations of DHA have been associated with impaired cognitive function, low hippocampal volumes, and increased amyloid deposition in the brain. Several studies have reported reduced brain DHA concentrations in Alzheimer's disease (AD) patients' brains. Although a number of epidemiological studies suggest that dietary DHA consumption may protect the elderly from developing cognitive impairment or dementia including AD, several review articles report an inconclusive association between omega-3 PUFAs intake and cognitive decline. The source of these inconsistencies might be because DHA is highly oxidizable and its accessibility to the brain is limited by the blood-brain barrier. Thus, there is a pressing need for new strategies to improve DHA brain supply. In the present study, we show for the first time that the intranasal administration of nanovectorized DHA reduces Tau phosphorylation and restores cognitive functions in two complementary murine models of AD. These results pave the way for the development of a new approach to target the brain with DHA for the prevention or treatment of this devastating disease.

9.
Neurobiol Aging ; 113: 118-130, 2022 05.
Article in English | MEDLINE | ID: mdl-35334439

ABSTRACT

In Alzheimer's disease (AD), hyper-phosphorylation and aggregation of tau correlate with clinical progression and represent a valid therapeutic target. A recent 20-year prospective study revealed an association between moderate to high frequency of Finnish sauna bathing and a lower incidence of dementia and AD, but the molecular mechanisms underlying these benefits remain uncertain. Here, we tested the hypothesis that sauna-like conditions could lower tau phosphorylation by increasing body temperature. We observed a decrease in tau phosphorylation in wild-type and hTau mice as well as in neuron-like cells when exposed to higher temperatures. These effects were correlated with specific changes in phosphatase and kinase activities, but not with inflammatory or heat shock responses. We also used a drug strategy to promote thermogenesis: topical application of menthol, which led to a sustained increase in body temperature in hTau mice, concomitant with a significant decrease in tau phosphorylation. Our results suggest that sauna-like conditions or menthol treatment could lower tau pathology through mild hyperthermia, and may provide promising therapeutic strategies for AD and other tauopathies.


Subject(s)
Alzheimer Disease , Steam Bath , Tauopathies , Alzheimer Disease/pathology , Animals , Menthol , Mice , Phosphorylation , Prospective Studies , Tauopathies/pathology , tau Proteins/metabolism
10.
Epilepsia ; 63(4): 919-935, 2022 04.
Article in English | MEDLINE | ID: mdl-35224720

ABSTRACT

OBJECTIVE: Although epilepsies and neurodegenerative disorders show pathophysiological similarities, their direct functional associations are unclear. Here, we tested the hypothesis that experimental seizures can induce tau hyperphosphorylation and amyloidogenic modifications over time, with intersections with neuroinflammation. METHODS: We used a model of mesial temporal lobe epilepsy (MTLE) where unilateral intrahippocampal injection of kainic acid (KA) in C57BL/6 mice elicits epileptogenesis and spontaneous focal seizures. We used a model of generalized status epilepticus (SE) obtained by intraperitoneal KA injection in C57BL/6 mice. We performed analyses and cross-comparisons according to a schedule of 72 h, 1 week, and 8 weeks after KA injection. RESULTS: In experimental MTLE, we show AT100, PHF1, and CP13 tau hyperphosphorylation during epileptogenesis (72 h-1 week) and long-term (8 weeks) during spontaneous seizures in the ipsilateral hippocampi, the epileptogenic zone. These pathological modifications extended to the contralateral hippocampus, a seizure propagating zone with no histological lesion or sclerosis. Two kinases, Cdk5 and GSK3ß, implicated in the pathological phosphorylation of tau, were activated. In this MTLE model, the induction of the amyloidogenic pathway (APP, C99, BACE1) was prominent and long-lasting in the epileptogenic zone. These Alzheimer's disease (AD)-relevant markers, established during seizure progression and recurrence, reciprocated an enduring glial (GFAP, Iba1) inflammation and the inadequate activation of the endogenous, anti-inflammatory, glucocorticoid receptor system. By contrast, a generalized SE episode provoked a predominantly transient induction of tau hyperphosphorylation and amyloidogenic markers in the hippocampus, along with resolving inflammation. Finally, we identified overlapping profiles of long-term hippocampal tau hyperphosphorylation by comparing MTLE to J20 mice, the latter a model relevant to AD. SIGNIFICANCE: MTLE and a generalized SE prompt persistent and varying tau hyperphosphorylation or amyloidogenic modifications in the hippocampus. In MTLE, an AD-relevant molecular trajectory intertwines with neuroinflammation, spatiotemporally involving epileptogenic and nonlesional seizure propagating zones.


Subject(s)
Epilepsy, Temporal Lobe , Status Epilepticus , Amyloid Precursor Protein Secretases/metabolism , Animals , Aspartic Acid Endopeptidases/metabolism , Disease Models, Animal , Hippocampus/pathology , Inflammation/metabolism , Kainic Acid/toxicity , Mice , Mice, Inbred C57BL , Seizures
11.
Neuroendocrinology ; 112(10): 982-997, 2022.
Article in English | MEDLINE | ID: mdl-34923495

ABSTRACT

INTRODUCTION: Among the risk factors identified in the sporadic forms of Alzheimer's disease (AD), environmental and lifestyle elements are of growing interest. Clinical observations suggest that stressful events can anticipate AD onset, while stress-related disorders can promote AD. Here, we tested the hypothesis that a chronic treatment with glucocorticoids is sufficient to trigger or exacerbate AD molecular hallmarks. METHODS: We first validated a rat model of experimental chronic glucocorticoids (GC) consumption (corticosterone [CORT] in drinking water for 4 weeks). Then, to evaluate the consequences of chronic GC consumption on the onset of amyloid-ß (Aß) toxicity, animals chronically treated with GC were intracerebroventricularly injected with an oligomeric solution of Aß25-35 (oAß) (acute model of AD). We evaluated AD-related cognitive deficits and pathogenic mechanisms, with a special emphasis on neuroinflammatory markers. RESULTS: Chronic CORT consumption caused the inhibition of the nonamyloidogenic pathways, the impairment of Aß clearance processes and the induction of amyloidogenic pathways in the hippocampus. The principal enzymes involved in glucocorticoid receptor activation and Tau phosphorylation were upregulated. Importantly, the AD-like phenotype triggered by chronic CORT was analogous to the one caused by oAß. These molecular commonalities across models were independent from inflammation, as chronic CORT was immunosuppressive while oAß was pro-inflammatory. When chronic CORT consumption anticipated the induction of the oAß pathology, we found a potentiation of neuroinflammatory processes associated with an exacerbation of synaptic and memory deficits but also an aggravation of AD-related hallmarks. DISCUSSION/CONCLUSION: This study unravels new functional outcomes identifying chronic CORT consumption as a main risk factor for AD and suggests that glucocorticoid-based therapies should be prescribed with caution in populations with AD risk.


Subject(s)
Alzheimer Disease , Drinking Water , Alzheimer Disease/metabolism , Animals , Corticosterone , Disease Models, Animal , Glucocorticoids/metabolism , Glucocorticoids/toxicity , Hippocampus/metabolism , Mice , Mice, Transgenic , Rats , Receptors, Glucocorticoid/metabolism , tau Proteins/metabolism
12.
FASEB J ; 34(1): 1150-1168, 2020 01.
Article in English | MEDLINE | ID: mdl-31914623

ABSTRACT

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis occurs early in Alzheimer's disease (AD), associated with elevated circulating glucocorticoids (GC) and glucocorticoid receptors (GR) signaling impairment. However, the precise role of GR in the pathophysiology of AD remains unclear. Using an acute model of AD induced by the intracerebroventricular injection of amyloid-ß oligomers (oAß), we analyzed cellular and behavioral hallmarks of AD, GR signaling pathways, processing of amyloid precursor protein, and enzymes involved in Tau phosphorylation. We focused on the prefrontal cortex (PFC), particularly rich in GR, early altered in AD and involved in HPA axis control and cognitive functions. We found that oAß impaired cognitive and emotional behaviors, increased plasma GC levels, synaptic deficits, apoptosis and neuroinflammatory processes. Moreover, oAß potentiated the amyloidogenic pathway and enzymes involved both in Tau hyperphosphorylation and GR activation. Treatment with a selective GR modulator (sGRm) normalized plasma GC levels and all behavioral and biochemical parameters analyzed. GR seems to occupy a central position in the pathophysiology of AD. Deregulation of the HPA axis and a feed-forward effect on PFC GR sensitivity could participate in the etiology of AD, in perturbing Aß and Tau homeostasis. These results also reinforce the therapeutic potential of sGRm in AD.


Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/chemistry , Receptors, Glucocorticoid/metabolism , tau Proteins/metabolism , Adrenal Cortex Hormones/chemistry , Amyloid beta-Protein Precursor/metabolism , Animals , Behavior, Animal , Disease Models, Animal , Glucocorticoids/metabolism , Homeostasis , Hypothalamo-Hypophyseal System , Male , Phosphorylation , Pituitary-Adrenal System , Rats , Rats, Sprague-Dawley , Signal Transduction
13.
Front Aging Neurosci ; 11: 269, 2019.
Article in English | MEDLINE | ID: mdl-31611783

ABSTRACT

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that has important health and economic impacts in the elderly. Despite a better understanding of the molecular mechanisms leading to the appearance of major pathological hallmarks (senile plaques and neurofibrillary tangles), effective treatments are still lacking. Sporadic AD forms (98% of all cases) are multifactorial, and a panoply of risk factors have been identified. While the major risk factor is aging, growing evidence suggests that chronic stress or stress-related disorders increase the probability to develop AD. An early dysregulation of the hypothalamic-pituitary-adrenal axis (HPA axis or stress axis) has been observed in patients. The direct consequence of such perturbation is an oversecretion of glucocorticoids (GC) associated with an impairment of its receptors (glucocorticoid receptors, GR). These steroids hormones easily penetrate the brain and act in synergy with excitatory amino acids. An overexposure could be highly toxic in limbic structures (prefrontal cortex and hippocampus) and contribute in the cognitive decline occurring in AD. GC and GR dysregulations seem to be involved in lots of functions disturbed in AD and a vicious cycle appears, where AD induces HPA axis dysregulation, which in turn potentiates the pathology. This review article presents some preclinical and clinical studies focusing on the HPA axis hormones and their receptors to fight AD. Due to its primordial role in the maintenance of homeostasis, the HPA axis appears as a key-actor in the etiology of AD and a prime target to tackle AD by offering multiple angles of action.

14.
FASEB J ; 33(12): 13998-14009, 2019 12.
Article in English | MEDLINE | ID: mdl-31618599

ABSTRACT

Immune changes occur in experimental and clinical epilepsy. Here, we tested the hypothesis that during epileptogenesis and spontaneous recurrent seizures (SRS) an impairment of the endogenous anti-inflammatory pathway glucocorticoid receptor (GR)-annexin A1 (ANXA1) occurs. By administrating exogenous ANXA1, we studied whether pharmacological potentiation of the anti-inflammatory response modifies seizure activity and pathophysiology. We used an in vivo model of temporal lobe epilepsy based on intrahippocampal kainic acid (KA) injection. Video-electroencephalography, molecular biology analyses on brain and peripheral blood samples, and pharmacological investigations were performed in this model. Human epileptic cortices presenting type II focal cortical dysplasia (IIa and b), hippocampi with or without hippocampal sclerosis (HS), and available controls were used to study ANXA1 expression. A decrease of phosphorylated (phospho-) GR and phospho-GR/tot-GR protein expression occurred in the hippocampus during epileptogenesis. Downstream to GR, the anti-inflammatory protein ANXA1 remained at baseline levels while inflammation installed and endured. In peripheral blood, ANXA1 and corticosterone levels showed no significant modifications during disease progression except for an early and transient increase poststatus epilepticus. These results indicate inadequate ANXA1 engagement over time and in these experimental conditions. By analyzing human brain specimens, we found that where significant inflammation exists, the pattern of ANXA1 immunoreactivity was abnormal because the typical perivascular ANXA1 immunoreactivity was reduced. We next asked whether potentiation of the endogenous anti-inflammatory mechanism by ANXA1 administration modifies the disease pathophysiology. Although with varying efficacy, administration of exogenous ANXA1 somewhat reduced the time spent in seizure activity as compared to saline. These results indicate that the anti-inflammatory GR-ANXA1 pathway is defective during experimental seizure progression. The prospect of pharmacologically restoring or potentiating this endogenous anti-inflammatory mechanism as an add-on therapeutic strategy for specific forms of epilepsy is proposed.-Zub, E., Canet, G., Garbelli, R., Blaquiere, M., Rossini, L., Pastori, C., Sheikh, M., Reutelingsperger, C., Klement, W., de Bock, F., Audinat, E., Givalois, L., Solito, E., Marchi, N. The GR-ANXA1 pathway is a pathological player and a candidate target in epilepsy.


Subject(s)
Annexin A1/metabolism , Epilepsy , Receptors, Glucocorticoid/metabolism , Animals , Annexin A1/genetics , Blood Cell Count , Brain/drug effects , Brain/metabolism , Corticosterone/metabolism , Gene Expression Regulation/drug effects , Gene Expression Regulation/physiology , Hippocampus , Humans , Inflammation/metabolism , Inflammation/pathology , Kainic Acid/administration & dosage , Kainic Acid/pharmacology , Mice , Mice, Inbred C57BL , Receptors, Glucocorticoid/genetics
15.
Front Neurosci ; 12: 739, 2018.
Article in English | MEDLINE | ID: mdl-30459541

ABSTRACT

Alzheimer's disease (AD) is the principal neurodegenerative pathology in the world displaying negative impacts on both the health and social ability of patients and inducing considerable economic costs. In the case of sporadic forms of AD (more than 95% of patients), even if mechanisms are unknown, some risk factors were identified. The principal risk is aging, but there is growing evidence that lifetime events like chronic stress or stress-related disorders may increase the probability to develop AD. This mini-review reinforces the rationale to consider major depressive disorder (MDD) as an important risk factor to develop AD and points the central role played by the hypothalamic-pituitary-adrenal (HPA) axis, glucocorticoids (GC) and their receptors (GR) in the etiology of MDD and AD. Several strategies directly targeting GR were tested to neutralize the HPA axis dysregulation and GC overproduction. Given the ubiquitous expression of GR, antagonists have many undesired side effects, limiting their therapeutic potential. However, a new class of molecules was developed, highly selective and acting as modulators. They present the advantage to selectively abrogate pathogenic GR-dependent processes, while retaining beneficial aspects of GR signaling. In fact, these "selective GR modulators" induce a receptor conformation that allows activation of only a subset of downstream signaling pathways, explaining their capacity to combine agonistic and antagonistic properties. Thus, targeting GR with selective modulators, alone or in association with current strategies, becomes particularly attractive and relevant to develop novel preventive and/or therapeutic strategies to tackle disorders associated with a dysregulation of the HPA axis.

16.
Front Cell Neurosci ; 12: 307, 2018.
Article in English | MEDLINE | ID: mdl-30254568

ABSTRACT

Environmental factors such as chemicals, stress and pathogens are now widely believed to play important roles in the onset of some brain diseases, as they are associated with neuronal impairment and acute or chronic inflammation. Alzheimer's disease (AD) is characterized by progressive synaptic dysfunction and neurodegeneration that ultimately lead to dementia. Neuroinflammation also plays a prominent role in AD and possible links to viruses have been proposed. In particular, the human immunodeficiency virus (HIV) can pass the blood-brain barrier and cause neuronal dysfunction leading to cognitive dysfunctions called HIV-associated neurocognitive disorders (HAND). Similarities between HAND and HIV exist as numerous factors involved in AD such as members of the amyloid and Tau pathways, as well as stress-related pathways or blood brain barrier (BBB) regulators, seem to be modulated by HIV brain infection, leading to the accumulation of amyloid plaques or neurofibrillary tangles (NFT) in some patients. Here, we summarize findings regarding how HIV and some of its proteins such as Tat and gp120 modulate signaling and cellular pathways also impaired in AD, suggesting similarities and convergences of these two pathologies.

17.
Oncotarget ; 9(28): 19688-19703, 2018 Apr 13.
Article in English | MEDLINE | ID: mdl-29731975

ABSTRACT

Plasma phospholipid transfer protein (PLTP) binds and transfers a number of amphipathic compounds, including phospholipids, cholesterol, diacylglycerides, tocopherols and lipopolysaccharides. PLTP functions are relevant for many pathophysiological alterations involved in neurodegenerative disorders (especially lipid metabolism, redox status, and immune reactions), and a significant increase in brain PLTP levels was observed in patients with Alzheimer's disease (AD) compared to controls. To date, it has not been reported whether PLTP can modulate the formation of amyloid plaques, i.e. one of the major histopathological hallmarks of AD. We thus assessed the role of PLTP in the AD context by breeding PLTP-deficient mice with an established model of AD, the J20 mice. A phenotypic characterization of the amyloid pathology was conducted in J20 mice expressing or not PLTP. We showed that PLTP deletion is associated with a significant reduction of cerebral Aß deposits and astrogliosis, which can be explained at least in part by a rise of Aß clearance through an increase in the microglial phagocytic activity and the expression of the Aß-degrading enzyme neprilysin. PLTP arises as a negative determinant of plaque clearance and over the lifespan, elevated PLTP activity could lead to a higher Aß load in the brain.

18.
Neurobiol Aging ; 45: 109-122, 2016 09.
Article in English | MEDLINE | ID: mdl-27459932

ABSTRACT

In Alzheimer's disease (AD), cognitive deficits and psychological symptoms are associated with an early deregulation of the hypothalamic-pituitary-adrenal axis. Here, in an acute model of AD, we investigated if antiglucocorticoid strategies with selective glucocorticoid receptor (GR) modulators (CORT108297 and CORT113176) that combine antagonistic and agonistic GR properties could offer an interesting therapeutic approach in the future. We confirm the expected properties of the nonselective GR antagonist (mifepristone) because in addition to restoring basal circulating glucocorticoids levels, mifepristone totally reverses synaptic deficits and hippocampal apoptosis processes. However, mifepristone only partially reverses cognitive deficit, effects of the hippocampal amyloidogenic pathway, and neuroinflammatory processes, suggesting limits in its efficacy. By contrast, selective GR modulators CORT108297 and CORT113176 at a dose of 20 and 10 mg/kg, respectively, reverse hippocampal amyloid-ß peptide generation, neuroinflammation, and apoptotic processes, restore the hippocampal levels of synaptic markers, re-establish basal plasma levels of glucocorticoids, and improve cognitive function. In conclusion, selective GR modulators are particularly attractive and may pave the way to new strategies for AD treatment.


Subject(s)
Alzheimer Disease/drug therapy , Amyloid beta-Peptides , Aza Compounds/therapeutic use , Heterocyclic Compounds, 4 or More Rings/therapeutic use , Hippocampus , Isoquinolines/therapeutic use , Molecular Targeted Therapy , Pyrazoles/therapeutic use , Receptors, Glucocorticoid/agonists , Receptors, Glucocorticoid/antagonists & inhibitors , Alzheimer Disease/chemically induced , Alzheimer Disease/metabolism , Alzheimer Disease/pathology , Amyloid beta-Peptides/metabolism , Amyloid beta-Peptides/toxicity , Animals , Aza Compounds/pharmacology , Cognitive Dysfunction/drug therapy , Disease Models, Animal , Dose-Response Relationship, Drug , Glucocorticoids/blood , Heterocyclic Compounds, 4 or More Rings/pharmacology , Hippocampus/metabolism , Hippocampus/pathology , Hypothalamo-Hypophyseal System , Isoquinolines/pharmacology , Male , Mifepristone/pharmacology , Mifepristone/therapeutic use , Pituitary-Adrenal System , Pyrazoles/pharmacology , Rats, Sprague-Dawley
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