[Biomarkers for early diagnosis of Alzheimer's disease: current update and future directions]. / Diagnostic biologique de la maladie d'Alzheimer: avancées, limites et perspectives.

INTRODUCTION: The increased prevalence of the sporadic form of Alzheimer's disease (AD) has become a significant health issue in the elderly population. The need for early diagnosis is imperative because this, along with the development of novel therapeutic treatments, would permit the rapid and perhaps more efficient treatment of these debilitating disorders early on. BACKGROUND: Over the last decade, the potential use of certain biomarkers in the cerebrospinal fluid (CSF), and more recently, in the plasma has been investigated. Among the candidates studied includes the neurotoxic amyloid beta peptide and the Tau protein. However, although these two proteins have been clearly shown to be directly related to the pathophysiology of this disorder, it has proven difficult to establish a clear relationship between plasma or CSF levels of Abeta and Tau and the incidence and severity of AD in patients. This is due in part to differences in methodologies related to the detection sensitivity, as well as the variations in the biological data and consequent interpretation of the biochemical and biological data. Peripheral cells, in particular platelets and skin fibroblasts, could be an alternative solution as peripheral biological markers for the early diagnosis of AD. These cells are easily accessible from patients. Furthermore, they would provide a means not only to validate potential therapeutic strategies, but also to study the mechanisms involved in the development of AD, including APP processing. PERSPECTIVES: A combined strategy using both a fundamental mechanistic and an analytical approach of patient peripheral cells will allow the identification of new biological markers for AD, and hence permit immediate therapeutic strategies to be implemented.

Diagnosis associated with Tau higher than 1200 pg/mL: Insights from the clinical and laboratory practice.

CONTEXT: Cerebrospinal fluid (CSF) biomarkers are valuable tools for the diagnosis of neurological diseases. We aimed to investigate within a retrospective multicentric study the final diagnosis associated with very high CSF Tau levels and to identify patterns of biomarkers that would differentiate them in clinical practice, to help clinical biologists into physicians' counseling. PATIENTS AND METHODS: Within the national multicentric network ePLM, we included 1743 patients from January 1, 2008, to December 31, 2013, with CSF biomarkers assayed by the same Innotest assays (protein Tau, phospho-Tau [pTau], and Aß 1-42). We identified 205 patients with protein Tau concentration higher than 1200 pg/mL and final diagnosis. RESULTS: Among those patients, 105 (51.2%) were suffering from Alzheimer's disease, 37 (18%) from sporadic Creuztfeldt-Jakob disease, and 63 (30.7%) from other neurological diseases including paraneoplastic/ central nervous system tumor, frontotemporal dementia, other diagnoses, amyloid angiopathy, Lewy body dementia, and infections of the central nervous system. Phospho-Tau, Aß1-42 and Aß1-42/pTau values differed significantly between the three groups of patients (p < .001). An Aß1-42/pTau ratio between 4.7 and 9.7 was suggestive of other neurological diseases (threshold in AD: 8.3). CSF 14-3-3 was useful to discriminate Alzheimer's disease from Creuztfeldt-Jakob disease in case of Aß1-42 concentrations <550 pg/mL or pTau>60 pg/mL. CONCLUSION: This work emphasizes the interest of a well-thought-out interpretation of CSF biomarkers in neurological diseases, particularly in the case of high Tau protein concentrations in the CSF.

Down-regulation of astroglial CYP2C, glucocorticoid receptor and constitutive androstane receptor genes in response to cocaine in human U373 MG astrocytoma cells.

Psychostimulant drugs abuse is associated with an increased risk of stroke. Cytochromes P450 (CYP), especially the astrocytic members of the CYP2C subfamily may play an important role in the modulation of cerebrovascular functions, by generating vasodilatator metabolites from arachidonic acid (AA). Our study examined the regulation of CYP2C genes in response to cocaine or amphetamine in the human astrocyte-like U373 MG cells, using reverse transcription-polymerase chain reaction (RT-PCR) and western-blot analysis. A treatment for 48h with increasing concentrations of cocaine caused a significant down-regulation of CYP2C8 and CYP2C9 genes and decreased the protein level. These effects were not observed with amphetamine. One mechanism of the CYP2C mRNA regulation implicates various specific receptors including glucocorticoid receptor (GR) and constitutive androstane receptor (CAR). Effects of cocaine on CYP2C were accompanied by a decrease in the GR and CAR gene expression suggesting that these nuclear receptors could be involved in the CYP2C repression by cocaine in the U373 MG cell line. These findings represent a possible molecular mechanism involved in the cerebrovascular risk associated with cocaine abuse.

Modifications of the endosomal compartment in peripheral blood mononuclear cells and fibroblasts from Alzheimer's disease patients.

Identification of blood-based biomarkers of Alzheimer's disease (AD) remains a challenge. Neuropathological studies have identified enlarged endosomes in post-mortem brains as the earliest cellular change associated to AD. Here the presence of enlarged endosomes was investigated in peripheral blood mononuclear cells from 48 biologically defined AD patients (25 with mild cognitive impairment and 23 with dementia (AD-D)), and 23 age-matched healthy controls using immunocytochemistry and confocal microscopy. The volume and number of endosomes were not significantly different between AD and controls. However, the percentage of cells containing enlarged endosomes was significantly higher in the AD-D group as compared with controls. Furthermore, endosomal volumes significantly correlated to [C(11)]PiB cortical index measured by positron emission tomography in the AD group, independently of the APOE genotype, but not to the levels of amyloid-beta, tau and phosphorylated tau measured in the cerebrospinal fluid. Importantly, we confirmed the presence of enlarged endosomes in fibroblasts from six unrelated AD-D patients as compared with five cognitively normal controls. This study is the first, to our knowledge, to report morphological alterations of the endosomal compartment in peripheral cells from AD patients correlated to amyloid load that will now be evaluated as a possible biomarker.

Astroglial CYP1B1 up-regulation in inflammatory/oxidative toxic conditions: IL-1beta effect and protection by N-acetylcysteine.

The present work aims to determine the relevance of an astrocytoma cell line U373 MG, for assessing the role of some astroglial cytochrome P450 in neurotoxicity and neuroprotection. CYP1B1, CYP2C8, CYP2C9, CYP2D6, CYP2J2, CYP2E1 and CYP4A11 mRNA were detected by reverse transcriptase-polymerase chain reaction in control U373 MG cell cultures. Among them we focused on CYP1B1 expression. After 48 h treatment with a range of concentrations of interleukin-1beta (1, 5, 10 ng/ml) used to simulate stress conditions, CYP1B1 mRNA expression was enhanced in a dose-dependent way. This increased expression was followed 24 h later by an increase in protein level, determined by Western-blot. N-acetylcysteine (NAC) partially inhibited this effect both on the mRNA and protein levels. As CYP1B1 activates procarcinogenic compounds to reactive metabolites, an increase in this P450 isoform will participate to toxic consequences of an inflammatory/oxidative stress. NAC will prevent this deleterious effect.

[Astrocytic cytochromes p450: an enzyme subfamily critical for brain metabolism and neuroprotection]. / Les cytochromes P450 astrocytaires, une famille d'enzymes clés dans le métabolisme cérébral et la neuroprotection.

INTRODUCTION: Astrocytes are involved in multiple brain functions in physiological conditions. Cytochromes P450 are expressed in astrocytes and play a role in brain metabolism and in neuroprotection. BACKGROUND: Although the levels of various cytochromes P450 in brain regions are low, these enzymes were reported to be expressed at relatively high level in astroglial cells and may play a critical role in the biotransformation of endogenous or exogenous compounds. Astroglial cytochromes P450 expression suggests a putative capacity to metabolize psychoactive or lipophilic xenobiotics in situ, associated with pharmacological and/or toxicological consequences. Astrocytes appear to be the most active steroidogenic cells in the brain, expressing neurosteroïdogenic cytochromes P450 and producing various neurosteroids. Cytochrome P450 epoxygenase enzymes, which catalyze the formation of vasoactive compounds are also present in astrocytes, contributing to the regulation of the cerebral blood flow. PERSPECTIVES AND CONCLUSION: This review underlines the crucial roles of astroglial cytochromes P450 in brain functions. Identification of the molecular mechanisms involved in the regulation of these enzymes could open therapeutic perspectives and improve our understanding in neuroprotection.

U373-MG response to interleukin-1beta-induced oxidative stress.

Oxidative stress has been involved in various neurological disorders and, in the central nervous system, astrocytes represent the cell type that contributes to neuroprotection via glutathione (GSH) metabolism, GSH-metabolizing enzymes like gamma-glutamyltransferase (GGT), and apoE secretion. In this study, using IL-1beta, a proinflammatory and prooxidant cytokine that is increased in numerous pathological situations, cells of astrocytoma cell line U373-MG were exposed to an oxidative stress, leading to c-Jun and c-Fos activation. IL-1beta decreased both GGT activity and intracellular GSH content and increased apoE secretion, initiating astroglial response to injury. We observed that antioxidants inhibit IL-1beta effects on c-Jun and c-Fos proteins, GGT activity and the GSH pool but not on apoE secretion. Our results allow us to conclude that neurological disorders associated with an IL-1beta-induced oxidative stress could be, at least experimentally, reversible in the presence of one antioxidant, N-acetylcysteine.