Postulated Vasoactive Neuropeptide Autoimmunity in Fatigue-Related Conditions: A Brief Review and Hypothesis

Disorders such as chronic fatigue syndrome (CFS) and gulf war syndrome (GWS) are characterised by prolonged fatigue and a range of debilitating symptoms of pain, intellectual and emotional impairment, chemical sensitivities and immunological dysfunction. Sudden infant death syndrome (SIDS) surprisingly may have certain features in common with these conditions. Post-infection sequelae may be possible contributing factors although ongoing infection is unproven. Immunological aberration may prove to be associated with certain vasoactive neuropeptides (VN) in the context of molecular mimicry, inappropriate immunological memory and autoimmunity

Etude des effets neuroprotecteurs du peptide PACAP sur la mort neuronale induite par les céramides au cours du développement du cervelet

La mort cellulaire programmée est un processus actif qui joue un rôle important au cours du développement du système nerveux central. Elle permet l élimination par apoptose des neurones générés en excès durant l embryogenèse afin d assurer un développement harmonieux du cerveau. L'apoptose observée au cours du développement met en jeu des processus similaires à ceux décrits lors de pathologies neurodégénératives. La caractérisation des mécanismes impliqués dans la régulation de l apoptose présente donc un intérêt pour le développement de stratégies thérapeutiques innovantes. Il a été montré que le pituitary adenylate cyclase-activating polypeptide (PACAP) exerce une action neuroprotectrice sur l apoptose des neurones en grain du cervelet. Parallèlement, la production de céramides par des cytokines a été décrite comme une voie d induction de l'apoptose. Ces observations suggèrent donc que le PACAP et certaines cytokines pourraient agir de façon opposée sur la décision de survie ou de mort de la cellule. Dans cette thèse, nous démontrons que le PACAP prévient l apoptose des neurones en grain du cervelet induite par les céramides et que ces effets impliquent la mitochondrie. Migration et apoptose des cellules granulaires sont intimement liées au cours du développement. Cependant, peu de données existent concernant les effets des céramides et du PACAP sur la migration des neurones et l élongation neuritique. Nous avons montré que le C2-céramide stimule la migration cellulaire et inhibe l élongation neuritique via une destructuration du cytosquelette. A l inverse, le PACAP réduit la vitesse de migration des neurones et augmente la croissance neuritique. Ces résultats montrent que le PACAP et les céramides régulent de façon opposée la différenciation et l apoptose des neurones en grain. Ils permettent de proposer de nouveaux concepts quant à l implication des cytokines et du PACAP au cours du développement et ouvrent de nouvelles perspectives thérapeutiques pour le traitement des lésions neurodégénératives.Programmed cell death is an active process which plays a key role during central nervous system ontogeny. During embryogenesis, neurons that are generated in excess are eliminated through an apoptotic process to allow harmonious brain development. Apoptosis which occurs during histogenesis involves the same mechanisms as those described during neurodegenerative injuries. The elucidation of the mechanisms regulating apoptosis is thus of crucial interest for the development of novel therapeutical strategies. It has been shown that the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) exerts neuroprotective effects on cerebellar granule cells. Concurrently, the production of the second messengers ceramides induced by cytokine has been described as a pathway inducing apoptosis. These obervations suggest that PACAP and cytokines may act in an opposite manner on cell death/survival decision.In this thesis, we demonstrate that PACAP prevents ceramide-induced cerebellar granule cell apoptosis and that these effects involve mitochondria. Migration and apoptosis of granule cells are closely linked during development. However, very few data are available concerning the effects of ceramides and PACAP on neuronal migration and neuritogenesis. We have demonstrated that C2-ceramide stimulates migration and inhibits neuritogenesis through cytoskeleton disorganization. In contrast, PACAP reduces cell migration and stimulates neurite outgrowth.These results show that PACAP and C2-ceramide exert opposite effects on differentiation and apoptosis of cerebellar granule cells. These data allow to propose new concepts concerning the involvement of cytokines and neuropeptides such as PACAP during development and open novel therapeutical perspectives for the treatment of neurodegenerative injuries.ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Selenoprotein T is a key player in ER proteostasis, endocrine homeostasis and neuroprotection

International audienceSelenoprotein T (SELENOT, SELT) is a thioredoxin-like enzyme anchored at the endoplasmic reticulum (ER) membrane, whose primary structure is highly conserved during evolution. SELENOT is abundant in embryonic tissues and its activity is essential during development since its gene knockout in mice is lethal early during embryogenesis. Although its expression is repressed in most adult tissues, SELENOT remains particularly abundant in endocrine organs such as the pituitary, pancreas, thyroid and testis, suggesting an important role of this selenoprotein in hormone production. Our recent studies showed indeed that SELENOT plays a key function in insulin and corticotropin biosynthesis and release by regulating ER proteostasis. Although SELENOT expression is low or undetectable in most cerebral structures, its gene conditional knockout in brain provokes anatomical alterations that impact mice behavior. This suggests that SELENOT also plays an important role in brain development and function. In addition, SELENOT is induced after injury in brain or liver and exerts a cytoprotective effect. Thus, the data gathered during the last ten years of intense investigation of this newly discovered thioredoxin-like enzyme point to an essential function during development and in adult endocrine organs or lesioned brain, most likely by regulating ER redox circuits that control homeostasis and survival of cells with intense metabolic activity

Granule Cell Survival is Deficient in PAC1(-/-) Mutant Cerebellum.

International audiencePACAP exerts neuroprotective effects during development, especially in the cerebellum where PAC1 receptor and ligand are both expressed. However, while previous studies using PACAP injections in postnatal animals defined trophic effects of exogenous peptide, the role of endogenous PACAP remains unexplored. Here, we used PAC1(-/-) mice to investigate the role of PACAP receptor signaling in postnatal day 7 cerebellum. There was no difference in DNA synthesis in the cerebellar EGL of PAC1(-/-) compared to wild type animals, assessed using thymidine incorporation and BrdU immunohistochemistry. In contrast, we found that a significant proportion of newly generated neurons were eliminated before they successfully differentiated in the granule cell layer. In aggregate, these results suggest that endogenous PACAP plays an important role in cell survival during cerebellar development, through the activation of the PAC1 receptor

Pituitary adenylate cyclase-activating polypeptide inhibits caspase-3 activity but does not protect cerebellar granule neurons against beta-amyloid (25-35)-induced apoptosis.

International audienceThe beta-amyloid (Abeta) peptide Abeta25-35 provokes apoptosis of cerebellar granule cells through activation of caspase-3 while the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) promotes granule cell survival by inhibiting caspase-3 activation through the intrinsic apoptotic pathway. The aim of the present study was to determine whether PACAP could prevent Abeta25-35 neurotoxicity by inhibiting caspase-3 activity. A 24-h exposure of cultured cerebellar granule cells to Abeta25-35 induced shrinkage of cell bodies, neurite retraction and alteration of mitochondrial activity. Administration of graded concentrations (10-80 microM) of Abeta25-35 induced a dose-related decrease of the number of living cells, and the neurotoxic effect was highly significant after a 24-h exposure to 80 microM Abeta25-35. Exposure of cerebellar granule cells to Abeta25-35 markedly enhanced caspase-3 but not caspase-9 activity. Co-incubation with 1 microM PACAP significantly reduced Abeta25-35-evoked caspase-3 activation. In contrast, PACAP did not prevent the deleterious effects of Abeta25-35 on mitochondrial potential and granule cell survival. Taken together, these data suggest that caspase-3 activation is not the main pathway activated by Abeta25-35 that leads to granule cell death. The results also demonstrate that PACAP cannot be considered as a potent neuroprotective factor against Abeta25-35-induced apoptosis in cerebellar granule neurons

Role of complement anaphylatoxin receptors (C3aR, C5aR) in the development of the rat cerebellum

International audienceThere is now strong evidence for non-immune or inflammatory functions of complement, notably in the central nervous system. In particular, it has been recently reported that the anaphylatoxin receptors C3aR and C5aR are transiently expressed in the cerebellar cortex of newborn rat, suggesting that anaphylatoxins are involved in the histogenesis of the cerebellum. In the present study, we have investigated the effects of C3aR and C5aR agonists and antagonists on the development of the cerebellum of 11-12-day-old rats in vivo and in vitro. Sub-dural injection of C3aR and C5aR agonists at the surface of the cerebellum transiently modified the thickness of the cortical layers. The C5aR agonist provoked an enlargement of the external granule cell layer (EGL) that was due to increased proliferation of immature granule neurons. Conversely, the C3aR agonist decreased the thickness of the EGL and increased the thickness of the internal granule cell layer (IGL), suggesting that C3a accelerates the migration process of granule cells from the EGL to the IGL. Video-microscopy examination of cultured granule neurons confirmed the role of C3aR in cell motility. These results provide clear evidence for the involvement of anaphylatoxin receptors in the histogenesis of the cerebellar cortex

Opposite regulation of the mitochondrial apoptotic pathway by C2-ceramide and PACAP through a MAP-kinase-dependent mechanism in cerebellar granule cells.

International audienceThe sphingomyelin-derived messenger ceramides provoke neuronal apoptosis through caspase-3 activation, while the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) promotes neuronal survival and inhibits caspase-3 activity. However, the mechanisms leading to the opposite regulation of caspase-3 by C2-ceramide and PACAP are currently unknown. Here, we show that PACAP prevents C2-ceramide-induced inhibition of mitochondrial potential and C2-ceramide-evoked cytochrome c release. C2-ceramide stimulated Bax expression, but had no effect on Bcl-2, while PACAP abrogated the action of C2-ceramide on Bax and stimulated Bcl-2 expression. The effects of C2-ceramide and PACAP on Bax and Bcl-2 were blocked, respectively, by the JNK inhibitor L-JNKI1 and the MEK inhibitor U0126. L-JNKI1 prevented the alteration of mitochondria induced by C2-ceramide while U0126 suppressed the protective effect of PACAP against the deleterious action of C2-ceramide on mitochondrial potential. Moreover, L-JNKI1 inhibited the stimulatory effect of C2-ceramide on caspase-9 and -3 and prevented C2-ceramide-induced cell death. U0126 blocked PACAP-induced Bcl-2 expression, abrogated the inhibitory effect of PACAP on ceramide-induced caspase-9 activity, and promoted granule cell death. The present study reveals that C2-ceramide and PACAP exert opposite effects on Bax and Bcl-2 through, respectively, JNK- and ERK-dependent mechanisms. These data indicate that the mitochondrial pathway plays a pivotal role in the pro- and anti-apoptotic effects of C2-ceramide and PACAP

Selenoprotein T Deficiency Leads to Neurodevelopmental Abnormalities and Hyperactive Behavior in Mice

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Ontogeny of PACAP receptors in the human cerebellum: perspectives of therapeutic applications.

International audienceIt is now well established that pituitary adenylate cyclase-activating polypeptide (PACAP) exerts anti-apoptotic and pro-differentiating actions during development of the rodent cerebellum. Cell signaling involved in the neurotrophic effects of PACAP has been precisely investigated. In particular, PACAP is a potent inhibitor of the mitochondrial apoptotic pathway through an ERK- and PKA-dependent mechanism. However, transposition of the neurodevelopmental activities of PACAP to the human cerebellum remains speculative, essentially because of the lack of data concerning the PACAP-ergic system. The present review is based on recent results that provide the first molecular, pharmacological and anatomical characterizations of PACAP receptors in the developing human cerebellum. It is now clearly established that the distribution pattern of PAC1-R and VPAC1-R mRNA in the human cerebellum is very similar to that already described in rodents. [(125)I]PACAP27 binding sites are closely associated with germinative neuroepithelia in fetal stages and with mature granule cells in infants and adults. Pharmacological characterization revealed that, in fetuses, PACAP binding sites exhibit a PAC1-R profile while, in adult patients, they correspond to a heterogeneous population of PAC1-R and VPAC(1/2)-R. Altogether, these data provide the first evidence that PACAP may exert neurodevelopmental functions in the human cerebellum