Cross-Talk between Oxysterols and Glucocorticoids: Differential Regulation of Secreted Phopholipase A2 and Impact on Oligodendrocyte Death

BACKGROUND: Oxysterols are oxidized forms of cholesterol. They have been shown to be implicated in cholesterol turnover, inflammation and in neurodegenerative diseases such as Alzheimer's disease and multiple sclerosis. Glial cells are targets of oxysterols: they inhibit astrocyte proliferation after brain injury, and we have previously shown that 25-hydroxycholesterol (25OH) provokes oligodendrocyte apoptosis and stimulates the expression of sPLA2 type IIA (sPLA2-IIA), which has a protective effect. METHODOLOGY/PRINCIPAL FINDINGS: As glucocorticoids are well-known for their anti-inflammatory effects, our aim was to understand their direct effects on oxysterol-induced responses in oligodendrocytes (sPLA2-IIA stimulation and apoptosis). We demonstrate that the synthetic glucocorticoid dexamethasone (Dex) abolishes the stimulation of sPLA2-IIA by 25-hydroxycholesterol (25-OH). This inhibition is mediated by the glucocorticoid receptor (GR), which decreases the expression of the oxysterol receptor Pregnane X Receptor (PXR) and interferes with oxysterol signaling by recruiting a common limiting coactivator PGC1alpha. Consistent with the finding that sPLA2-IIA can partially protect oligodendrocytes against oxysterol-triggered apoptosis, we demonstrate here that the inhibition of sPLA2-IIA by Dex accelerates the apoptotic phenomenon, leading to a shift towards necrosis. We have shown by atomic force microscopy and electron microscopy that 25-OH and Dex alters oligodendrocyte shape and disorganizes the cytoplasm. CONCLUSIONS/SIGNIFICANCE: Our results provide a new understanding of the cross-talk between oxysterol and glucocorticoid signaling pathways and their respective roles in apoptosis and oligodendrocyte functions

Shift from extracellular signal-regulated kinase to AKT/cAMP response element-binding protein pathway increases survival-motor-neuron expression in spinal-muscular-atrophy-like mice and patient cells

Spinal muscular atrophy (SMA), a recessive neurodegenerative disease, is characterized by the selective loss of spinal motor neurons. No available therapy exists for SMA, which represents one of the leading genetic causes of death in childhood. SMA is caused by a mutation of the survival-of-motor-neuron 1 (SMN1) gene, leading to a quantitative defect in the survival-motor-neuron (SMN) protein expression. All patients retain one or more copies of the SMN2 gene, which modulates the disease severity by producing a small amount of stable SMN protein. We reported recently that NMDA receptor activation, directly in the spinal cord, significantly enhanced the transcription rate of the SMN2 genes in a mouse model of very severe SMA (referred as type 1) by a mechanism that involved AKT/CREB pathway activation. Here, we provide the first compelling evidence for a competition between the MEK/ERK/Elk-1 and the phosphatidylinositol 3-kinase/AKT/CREB signaling pathways for SMN2 gene regulation in the spinal cord of type 1 SMA-like mice. The inhibition of the MEK/ERK/Elk-1 pathway promotes the AKT/CREB pathway activation, leading to (1) an enhanced SMN expression in the spinal cord of SMA-like mice and in human SMA myotubes and (2) a 2.8-fold lifespan extension in SMA-like mice. Furthermore, we identified a crosstalk between ERK and AKT signaling pathways that involves the calcium-dependent modulation of CaMKII activity. Together, all these data open new perspectives to the therapeutic strategy for SMA patients.This project was supported by the Association Française contre les Myopathies. J.B. is the recipients of a fellowship from the Ministry of Research and Technology, and F.Chal. is the recipient of a fellowship from AXA Research Fund/Garches Foundation.Peer reviewe

Novel therapeutic strategies for spinal osteosarcomas

At the dawn of the third millennium, cancer has become the bane of twenty-first century man, and remains a predominant public health burden, affecting welfare and life expectancy globally. Spinal osteogenic sarcoma, a primary spinal malignant tumor, is a rare and challenging neoplastic disease to treat. After the conventional therapeutic modalities of chemotherapy, radiation and surgery have been exhausted, there is currently no available alternative therapy in managing cases of spinal osteosarcoma. The defining signatures of tumor survival are characterised by cancer cell ability to stonewall immunogenic attrition and apoptosis by various means. Some of these biomarkers, namely immune-checkpoints, have recently been exploited as druggable targets in osteosarcoma and many other different cancers. These promising strides made by the use of reinvigorated immunotherapeutic approaches may lead to significant reduction in spinal osteosarcoma disease burden and corresponding reciprocity in increase of survival rates. In this review, we provide the background to spinal osteosarcoma, and proceed to elaborate on contribution of the complex ecology within tumor microenvironment giving arise to cancerous immune escape, which is currently receiving considerable attention. We follow this section on the tumor microenvironment by a brief history of cancer immunity. Also, we draw on the current knowledge of treatment gained from incidences of osteosarcoma at other locations of the skeleton (long bones of the extremities in close proximity to the metaphyseal growth plates) to make a case for application of immunity-based tools, such as immune-checkpoint inhibitors and vaccines, and draw attention to adverse upshots of immune-checkpoint blockers as well. Finally, we describe the novel biotechnique of CRISPR/Cas9 that will assist in treatment approaches for personalized medication.This work is funded by a grant (MPP 320133) from the American University of Beirut to Dr. Ali H. Eid

Wnt/β-Catenin Signaling Pathway Is a Direct Enhancer of Thyroid Transcription Factor-1 in Human Papillary Thyroid Carcinoma Cells

The Wnt/β-catenin signaling pathway is involved in the normal development of thyroid gland, but its disregulation provokes the appearance of several types of cancers, including papillary thyroid carcinomas (PTC) which are the most common thyroid tumours. The follow-up of PTC patients is based on the monitoring of serum thyroglobulin levels which is regulated by the thyroid transcription factor 1 (TTF-1): a tissue-specific transcription factor essential for the differentiation of the thyroid. We investigated whether the Wnt/β-catenin pathway might regulate TTF-1 expression in a human PTC model and examined the molecular mechanisms underlying this regulation. Immunofluorescence analysis, real time RT-PCR and Western blot studies revealed that TTF-1 as well as the major Wnt pathway components are co-expressed in TPC-1 cells and human PTC tumours. Knocking-down the Wnt/β-catenin components by siRNAs inhibited both TTF-1 transcript and protein expression, while mimicking the activation of Wnt signaling by lithium chloride induced TTF-1 gene and protein expression. Functional promoter studies and ChIP analysis showed that the Wnt/β-catenin pathway exerts its effect by means of the binding of β-catenin to TCF/LEF transcription factors on the level of an active TCF/LEF response element at [−798, −792 bp] in TTF-1 promoter. In conclusion, we demonstrated that the Wnt/β-catenin pathway is a direct and forward driver of the TTF-1 expression. The localization of TCF-4 and TTF-1 in the same area of PTC tissues might be of clinical relevance, and justifies further examination of these factors in the papillary thyroid cancers follow-up

Early variations in white matter microstructure and depression outcome in adolescents with subthreshold-depression

Objective: White matter microstructure alterations have recently been associated with adolescence depressive episodes, but it is unknown whether they predate depression. We investigated whether subthreshold-depression in adolescence is associated with white matter microstructure variations and whether they relate to depression outcome.Method: Adolescents with subthreshold-depression (n=96) and healthy controls (n=336), drawn from a community-based cohort, were compared using diffusion tensor imaging and whole-brain tractbased spatial statistics (TBSS) at age 14 to assess white matter microstructure. They were followedup at age 16 to assess depression. Probabilistic tractography was used to reconstruct white matter streamlines from the TBSS analysis resulting regions, and along bundles implicated in emotion regulation, the uncinate fasciculus and the cingulum. We searched for mediating effects of white matter microstructure on the relationship between baseline subthreshold-depression and depression at follow-up, and then explored the specificity of the findings.Results: Lower fractional anisotropy (FA) and higher radial diffusivity were found in the anterior corpus callosum in the adolescents with subthreshold-depression. Tractography analysis showed that they also had lower FA in the right cingulum streamlines, along with lower FA and higher mean diffusivity in tracts connecting the corpus callosum to the anterior cingulate cortex. The relation between baseline subthreshold-depression and follow-up depression was mediated by FA values in the latter tracts, and lower FA values in those tracts distinctively predicted higher individual risk for depression.Conclusions: Early FA variations in tracts projecting from the corpus callosum to the anterior cingulate cortex might denote higher risk of transition to depression in adolescents

Early variations in white matter microstructure and depression outcome in adolescents with subthreshold-depression

Objective: White matter microstructure alterations have recently been associated with adolescence depressive episodes, but it is unknown whether they predate depression. We investigated whether subthreshold-depression in adolescence is associated with white matter microstructure variations and whether they relate to depression outcome. Method: Adolescents with subthreshold-depression (n=96) and healthy controls (n=336), drawn from a community-based cohort, were compared using diffusion tensor imaging and whole-brain tractbased spatial statistics (TBSS) at age 14 to assess white matter microstructure. They were followedup at age 16 to assess depression. Probabilistic tractography was used to reconstruct white matter streamlines from the TBSS analysis resulting regions, and along bundles implicated in emotion regulation, the uncinate fasciculus and the cingulum. We searched for mediating effects of white matter microstructure on the relationship between baseline subthreshold-depression and depression at follow-up, and then explored the specificity of the findings. Results: Lower fractional anisotropy (FA) and higher radial diffusivity were found in the anterior corpus callosum in the adolescents with subthreshold-depression. Tractography analysis showed that they also had lower FA in the right cingulum streamlines, along with lower FA and higher mean diffusivity in tracts connecting the corpus callosum to the anterior cingulate cortex. The relation between baseline subthreshold-depression and follow-up depression was mediated by FA values in the latter tracts, and lower FA values in those tracts distinctively predicted higher individual risk for depression. Conclusions: Early FA variations in tracts projecting from the corpus callosum to the anterior cingulate cortex might denote higher risk of transition to depression in adolescents

Identification and characterization of TRO19622 (cholest-4-en-3-one, oxime), a novel drug candidate for amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive death of cortical and spinal motor neurons, for which there is no effective treatment. Using a cell-based assay for compounds capable of preventing motor neuron cell death in vitro, a collection of about 40,000 low molecular weight compounds was screened to identify potential small-molecule therapeutics. We report the identification of cholest-4-en-3-one, oxime (TRO19622) as a potential drug candidate for the treatment of ALS. In vitro, TRO19622 promoted motor neuron survival in the absence of trophic support in a dose-dependent manner. In vivo, TRO19622 rescued motor neurons from axotomy-induced cell death in neonatal rats and promoted nerve regeneration following sciatic nerve crush in mice. In SOD1(G93A) transgenic mice, a model of familial ALS, TRO19622 treatment improved motor performance, delayed the onset of the clinical disease, and extended survival. TRO19622 bound directly to two components of the mitochondrial permeability transition pore: the voltage-dependent anion channel (VDAC) and the translocator protein (or peripheral benzodiazepine receptor), suggesting a potential mechanism for its neuroprotective activity. TRO19622 may have therapeutic potential for ALS and other motor neuron and neurodegenerative diseases

Rôle des voies Wnt dans la régulation des gènes de la myéline et le cytosquelette des cellules de Schwann

Les cellules de Schwann sont responsables de la myélinisation du système nerveuxpériphérique. C est un phénomène complexe et finement régulé. En effet, des altérationsde l expression touchant les protéines de la myéline périphérique (P0 et PMP22)peuvent provoquer des pathologies comme la Charcot Marie Tooth. Par ailleurs, lescellules de Schwann subissent d importantes modifications de leur cytosquelette aucours du processus de myélinisation.Nous avons identifié la voie Wnt/b caténine comme directement impliquées dansla régulation de l expression des gènes de la myéline P0 et PMP22 à la fois in vitro maiségalement in vivo. De plus, nous avons initié la démonstration de l implication de la voieWnt non canonique au cours de ce même processus. Par ailleurs, nous avons montré queles ligands Wnts aussi bien canoniques que non canoniques pouvaient provoquerl allongement des extensions des cellules de Schwann. Le chlorure de lithium est uninhibiteur de la GSK3b, mimant l activation de la voie Wnt/b caténine. Il provoque unimportant allongement des cellules de Schwann accompagné de profonds remaniementsde l architecture interne. Par la suite nous nous sommes intéressés aux effets d unelésion sur la remyélinisation. La voie Wnt/b caténine est réactivée par une lésion in vitrotandis que le lithium accélère la récupération fonctionnelle du battement des vibrissesde souris après pincement du nerf facial, améliore les structures de la gaine de myélineet induit l expression des gènes de la myéline in vivo.ConclusionNotre travail a mis en évidence le rôle majeur des voies Wnt canoniques et noncanoniques dans la régulation de l expression de gènes de la myéline et dans lecytosquelette des cellules de Schwann.The myelination is performed by Schwann cells in the peripheral nervous system.Myelination involves the extension of large sheaths of membranes and their wrapping around axons, accompanied by the coordinated synthesis of a variety of myelin components, including myelin specific proteins (MPZ and PMP22).We identified the Wnt/b caténin pathway as an essential and direct driver of myelin gene expression and myelinogenesis. Moreover, we identified non canonical Wnt protein as regulators of myelin genes expression MPZ and PMP22. Canonical and non canonical Wnt protein elongate the Schwann cells in vitro by microtubules stabilizationmechanisms.We used lithium chloride, an inhibitor of GSK3b to test either effects on Schwann cells cytoskeleton and recovery after nerve crash in vivo. Lithium chloride provokes Schwann cells elongation and biochemicals modifications by enhencing cholesterol as we show by IR spectroscopy. Lithium chloride accelerates the recovery of the whisker mouvements after nerve crash, provokes the remyelination of sciatic neve after crush and stimulates myelin genes expression.ConclusionWe have identified Wnt pathways as direct driver of myelin genes expression and important for cytoskeleton stabolization. Our findings, open new perspectivesin the treatment of nerves demyelination by administration of GSK3binhibitors like lithium.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Implication des stéroïdes et de la signalisation Wnt dans les cellules Gliales (Incidence sur la myélinisation et l'inflammation)

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF