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Publications (7)34.76 Total impact

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    ABSTRACT: Apoptosis is a regulated process, leading to cell death, which is involved in several pathologies including neurodegenerative diseases and stroke. Caspase-3 is a key enzyme of the apoptotic pathway and is considered as a major target for the treatment of abnormal cell death. Sensitive and non-invasive methods to monitor caspase-3 activity in cells and in the brain of living animals are needed to test the efficiency of novel therapeutic strategies. In the present study, we have biochemically characterized a caspase-3 far-red fluorescent probe, QCASP3.2, that can be used to detect apoptosis in vivo. The specificity of cleavage of QCASP3.2 was demonstrated using recombinant caspases and protease inhibitors. The functionality of the probe was also established in cerebellar neurons cultured in apoptotic conditions. QCASP3.2 did not exhibit any toxicity and appeared to accurately reflect the induction and inhibition of caspase activity by H2O2 and PACAP, respectively, both in cell lysates and in cultured neurons. Finally, intravenous injection of the probe after cerebral ischemia revealed activation of caspase-3 in the infarcted hemisphere. Thus, the present study demonstrates that QCASP3.2 is a suitable probe to monitor apoptosis both in vitro and in vivo and illustrates some of the possible applications of this caspase-3 fluorescent probe.
    Journal of Molecular Neuroscience 05/2014; · 2.89 Impact Factor
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    ABSTRACT: Urotensin II (UII) and Urotensin II-related peptide (URP) are structurally related paralogue peptides which exert peripheral and central effects. UII binding sites have been partly described in brain, and those of URP have never been reported. We exhaustively compared [(125) I]-UII and -URP binding site distributions in the adult rat brain, and found that they fully overlapped at the regional level. We observed UII/URP binding sites in structures lining ventricles, comprising the sphenoid nucleus and cell rafts scattered on a line joining the fourth ventricle and its lateral recess. After injection of UII and URP in the lateral ventricle, we observed c-Fos-positive cell nuclei in areas close to the fourth ventricle, indicating that these receptors are functional. Different c-Fos-containing cell populations were activated. They were all positive for vimentin and GFAP, excluding the possibility of their ependymal nature. In conclusion, this study demonstrated that UII and URP binding sites are totally overlapping and unraveled that these sites were functional in a number of regions bordering the third and fourth ventricles. These data support a role for UII/URP at the interface between brain parenchyma and cerebrospinal fluid. J. Comp. Neurol., 2014. © 2014 Wiley Periodicals, Inc.
    The Journal of Comparative Neurology 01/2014; · 3.66 Impact Factor
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    ABSTRACT: Hypothalamic glucose-sensing is involved in the control of feeding behavior and peripheral glucose homeostasis, and glial cells are suggested to play an important role in this process. Diazepam-binding inhibitor (DBI) and its processing product the octadecaneuropeptide (ODN), collectively named endozepines, are secreted by astroglia, and ODN is a potent anorexigenic factor. Therefore, we investigated the involvement of endozepines in brain glucose-sensing. First, we showed that intracerebroventricular administration of glucose in rats increases DBI expression in hypothalamic glial-like tanycytes. We then demonstrated that glucose stimulates endozepine secretion from hypothalamic explants. Feeding experiments indicate that the anorexigenic effect of central administration of glucose was blunted by coinjection of an ODN antagonist. Conversely, the hyperphagic response elicited by central glucoprivation was suppressed by an ODN agonist. The anorexigenic effects of centrally injected glucose or ODN agonist were suppressed by blockade of the melanocortin-3/4 receptors, suggesting that glucose-sensing involves endozepinergic control of the melanocortin pathway. Finally, we found that brain endozepines modulate blood glucose levels, suggesting their involvement in a feedback loop controlling whole-body glucose homeostasis. Collectively, these data indicate that endozepines are a critical relay in brain glucose-sensing and potentially new targets in treatment of metabolic disorders.
    Diabetes 11/2012; · 7.90 Impact Factor
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    ABSTRACT: Selenoproteins contain the essential trace element selenium whose deficiency leads to major disorders including cancer, male reproductive system failure, or autoimmune thyroid disease. Up to now, 25 selenoprotein-encoding genes were identified in mammals, but the spatiotemporal distribution, regulation, and function of some of these selenium-containing proteins remain poorly documented. Here, we found that selenoprotein T (SelT), a new thioredoxin-like protein, is regulated by the trophic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) in differentiating but not mature adrenomedullary cells. In fact, our analysis revealed that, in rat, SelT is highly expressed in most embryonic structures, and then its levels decreased progressively as these organs develop, to vanish in most adult tissues. In the brain, SelT was abundantly expressed in neural progenitors in various regions such as the cortex and cerebellum but was undetectable in adult nervous cells except rostral migratory-stream astrocytes and Bergmann cells. In contrast, SelT expression was maintained in several adult endocrine tissues such as pituitary, thyroid, or testis. In the pituitary gland, SelT was found in secretory cells of the anterior lobe, whereas in the testis, the selenoprotein was present only in spermatogenic and Leydig cells. Finally, we found that SelT expression is strongly stimulated in liver cells during the regenerative process that occurs after partial hepatectomy. Taken together, these data show that SelT induction is associated with ontogenesis, tissue maturation, and regenerative mechanisms, indicating that this PACAP-regulated selenoprotein may play a crucial role in cell growth and activity in nervous, endocrine, and metabolic tissues.
    Endocrinology 09/2011; 152(11):4322-35. · 4.72 Impact Factor
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    ABSTRACT: It is now established that the development of the CNS requires equilibrium between cell survival and apoptosis. Pituitary adenylate cyclase-activating polypeptide (PACAP) exerts a powerful protective effect on cerebellar granule cells by inhibiting the caspase 3. In contrast, Fas ligand (FasL) plays an essential role during ontogenesis in eliminating supernumerary neurons by apoptosis. To determine if PACAP and FasL interact during cerebellar development, we characterized the effects of these factors on cerebellar morphogenesis and caspase 3 activity in PACAP+/+ and PACAP-/- mice. First, we demonstrated in vivo that PACAP is able to reverse the diminution of internal granule cell layer thickness induced by FasL in PACAP+/+ and PACAP-/- mice. Second, ex vivo and immunohistochemical studies revealed that interaction between FasL and PACAP occurs through the caspase 3 activity. Third, behavioural study showed a significant difference for the PACAP + FasL group in the righting reflex test at P8 which does not persist at P60. Finally, a time course study revealed that the pro-apoptotic effect of FasL characterized at P8 was followed by a progressive compensatory mechanism in caspase 3 activity and bromodeoxyuridine incorporation. These data suggest that PACAP and FasL interact during cerebellar development to control apoptosis of granule cells and may affect some motor cerebellar functions.
    Journal of Neurochemistry 04/2010; 113(2):329-40. · 3.97 Impact Factor
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    ABSTRACT: 26RFa is a hypothalamic RFamide neuropeptide that was identified as the endogenous ligand of the orphan G protein-coupled receptor, GPR103, and that stimulates appetite in mice. Up until now, the mechanism of action of 26RFa in the hypothalamic control of food intake remains unknown. The high density of GPR103 in the arcuate nucleus (Arc) prompted us to investigate, in the present study, the effects of 26RFa on the rat neuropeptide Y (NPY)/proopiomelanocortin (POMC) system. Intracerebroventricular injection of 26RFa stimulated NPY expression and release in the basal hypothalamus, whereas it decreased POMC expression and alpha-MSH release, and these effects were associated with an increase in food intake. A double in situ hybridization procedure indicated that the 26RFa receptor is present in NPY neurons of the Arc, but not in POMC neurons. Central administration of NPY Y1 and Y5 receptor antagonists abolished the inhibitory effects of 26RFa on POMC expression and alpha-MSH release, and reversed 26RFa-induced food consumption. Finally, 26RFa antagonized the effects of leptin on NPY expression and release, POMC expression and alpha-MSH release, and food intake. Altogether, the present data demonstrate for the first time that 26RFa exerts its orexigenic activity by stimulating the release of NPY in the Arc, which in turn inhibits POMC neurons by activating the Y1 and Y5 receptors. It is also suggested that the balance 26RFa/leptin is an important parameter in the maintenance of energy homeostasis.
    Endocrinology 02/2009; 150(5):2342-50. · 4.72 Impact Factor
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    ABSTRACT: An increase in circulating catecholamine levels represents one of the mechanisms whereby organisms cope with stress. In the periphery, catecholamines mainly originate from the sympathoadrenal system. As we reported, in addition to the central control through cholinergic innervation, a local gap junction-delineated route between adrenal chromaffin cells contributes to catecholamine exocytosis. Here, we investigated whether this intercellular communication is modified when the hormonal demand is increased as observed during cold stress. Our results show that in cold exposed rats, gap-junctional communication undergoes a functional plasticity, as evidenced by an increased number of dye-coupled cells. Of a physiological interest is that this upregulation of gap-junctional coupling results in the appearance of a robust electrical coupling between chromaffin cells that allows the transmission of action potentials between coupled cells. This enhancement of gap-junctional communication parallels an increase in expression levels of connexin36 (Cx36) and connexin43 (Cx43) proteins. Both transcriptional and posttranslational mechanisms are involved because Cx36 transcripts are increased in stressed rats and the expression of the scaffolding protein zonula occludens-1, known to interact with both Cx36 and Cx43, is also upregulated. Consistent with an upregulated coupling extent in stressed rats, the cytosolic Ca(2+) concentration rises triggered in a single cell by an iontophoretic application of nicotine occur simultaneously in several neighboring cells. These results describe for the first time a functional plasticity of junctional coupling between adult chromaffin cells that should be crucial for adaptation to stress or sensitization to subsequent stressors.
    Journal of Neuroscience 07/2008; 28(26):6616-26. · 6.91 Impact Factor