IGF-I protects cortical neurons against ceramide-induced apoptosis via activation of the PI-3K/Akt and ERK pathways; is this protection independent of CREB and Bcl-2?

Current understanding of IGF-I-mediated neuroprotection implies the activation of phosphatidylinositol-3-kinase (PI-3K), which leads to the activation of Akt/Protein Kinase B. In non-neuronal cells, Akt phosphorylates and activates the transcription factor CREB, implicated in the transcription of the anti-apoptotic bcl-2 gene. This paper further analyses the anti-apoptotic IGF-I action in neurons. We show that IGF-I protects cortical neurons against ceramide-induced apoptosis. Ceramide decreases Akt phosphorylation during apoptotic process whereas a simultaneous treatment with IGF-I increases Akt phosphorylation. Analysis of the signal transduction pathways revealed that IGF-I induces CREB phosphorylation via PI-3K and ERK, whereas simultaneous ceramide and IGF-I treatment decreases CREB phosphorylation. Although an overexpression of Bcl-2 protects cortical neurons against ceramide-induced apoptosis, our data indicate that the Bcl-2 protein level is not modulated during IGF-I, ceramide and/or LY294002 treatment. In consequence, we demonstrated that IGF protects neurons against ceramide-induced apoptosis and that IGF-I protection involves the PI-3K/Akt and ERK pathways; this protection may be independent of CREB and Bcl-2

Contribution à l'étude de la variabilité géographique des Cèdres

International audienc

A novel probabilistic risk analysis to determine the vulnerability of ecosystems to extreme climatic events

We present a simple method of probabilistic risk analysis for ecosystems. The only requirements are time series — modelled or measured — of environment and ecosystem variables. Risk is defined as the product of hazard probability and ecosystem vulnerability. Vulnerability is the expected difference in ecosystem performance between years with and without hazardous conditions. We show an application to drought risk for net primary productivity of coniferous forests across Europe, for both recent and future climatic conditions

Degree of Coordination between Breathing and Rhythmic Arm Movements During Hand Rim Wheelchair Propulsion

International audienc

[Anatomical and histological study of the uterosacral ligament: practical surgical consequences]

International audienceOBJECTIVE: To define the vascular and nervous relationships of the uterosacral ligament and to analyze histologically its content for a better description of this structure. MATERIALS AND METHODS: Three fresh fetal cadavers, three embalmed and one fresh adult cadavers were used. The anatomical relationships of the uterosacral ligament were studied by dissecting one fresh fetal pelvis and two embalmed adult pelves. By histological and immunohistological examinations, eight biopsies of the cervical origin of the complexe ligamentaire utérosacral (USLC) were analyzed: four from fresh fetuses, two from a fresh adult cadaver and two from an embalmed adult cadaver. The specimens were stained with haematoxylin eosin safran (HES) coloration, with antinervous cell specific antibodies (PS100) and with antismooth muscle actine antibodies (to visualize vessel walls) before examination under optical microscope. RESULTS: On anatomic examination, the uterosacral ligament was covered by the visceral pelvic fascia. By removing this fascia, the uterosacral ligament appeared to be a condensation of nervous fibers made up of hypogastric and pelvic nerves forming the hypogastric plexus. Histologically, the uterosacral ligament contained connective tissue, nervous fibers, sympathetic nodes, vessels and fatty tissue. No structured ligamentous organization was identified. CONCLUSION: The uterosacral "ligament" is in fact a "ligament complex" integrating connective tissue as well as nervous and vascular elements. Radical wide excisions of the USLC during cancer or endometriosis surgery and uterosacral suspension during pelvic floor reconstructive surgery should be performed with caution in order to preserve pelvic innervation

Phosphorylation of mutant huntingtin at serine 116 modulates neuronal toxicity.

Phosphorylation has been shown to have a significant impact on expanded huntingtin-mediated cellular toxicity. Several phosphorylation sites have been identified on the huntingtin (Htt) protein. To find new potential therapeutic targets for Huntington's Disease (HD), we used mass spectrometry to identify novel phosphorylation sites on N-terminal Htt, expressed in HEK293 cells. Using site-directed mutagenesis we introduced alterations of phosphorylation sites in a N586 Htt construct containing 82 polyglutamine repeats. The effects of these alterations on expanded Htt toxicity were evaluated in primary neurons using a nuclear condensation assay and a direct time-lapse imaging of neuronal death. As a result of these studies, we identified several novel phosphorylation sites, validated several known sites, and discovered one phospho-null alteration, S116A, that had a protective effect against expanded polyglutamine-mediated cellular toxicity. The results suggest that S116 is a potential therapeutic target, and indicate that our screening method is useful for identifying candidate phosphorylation sites

Activation of the JNK-c-Jun pathway during the early phase of neuronal apoptosis induced by PrP106-126 and prion infection.

Prion diseases are neurodegenerative pathologies characterized by apoptotic neuronal death. Although the late execution phase of neuronal apoptosis is beginning to be characterized, the sequence of events occurring during the early decision phase is not yet well known. In murine cortical neurons in primary culture, apoptosis was first induced by exposure to a synthetic peptide homologous to residues 106-126 of the human prion protein (PrP), PrP106-126. Exposure to its aggregated form induced a massive neuronal death within 24 h. Apoptosis was characterized by nuclear fragmentation, neuritic retraction and fragmentation and activation of caspase-3. During the early decision phase, reactive oxygen species were detected after 3 h. Using immunocytochemistry, we showed a peak of phosphorylated c-Jun-N-terminal kinase (JNK) translocation into the nucleus after 8 h, along with the activation of the nuclear c-Jun transcription factor. Both pharmacological inhibition of JNK by SP600125 and overexpression of a dominant negative form of c-Jun significantly reduced neuronal death, while the MAPK p38 inhibitor SB203580 had no effect. Apoptosis was also studied after exposure of tg338 cortical neurons in primary culture to sheep scrapie agent. In this model, prion-induced neuronal apoptosis gradually increased with time and induced a 40% cell death after 2 weeks exposure. Immunocytochemical analysis showed early c-Jun activation after 7 days. In summary, the JNK-c-Jun pathway plays an important role in neuronal apoptosis induced by PrP106-126. This pathway is also activated during scrapie infection and may be involved in prion-induced neuronal death. Pharmacological blockade of early pathways opens new therapeutic prospects for scrapie PrP-based pathologies

Identified phosphorylarion peptides.

<p>Identified phosphorylarion peptides.</p

Time lapse imaging of toxicity of N586 constructs.

<p>Primary cortical neurons were co-transfected at DIV5. Beginning 24 hours after transfection, GFP positive neurons were imaged every 10 mn for 10 hours. (A) Representative images of cells transfected with N586-22Q (top row), N586-82Q (middle row), or N586-82Q S116A (bottom row) at t = 0 (left column), t = 5 h (center column), and t = 10 h (right column). (B) Quantification of cell survival. For each time point cells were given the value of 100 if alive and 0 if dead. Results are expressed as mean ± sem. n = 200 cells analyzed in 5 independent experiments.</p