No description available.

The Endocannabinoid system has been found in the gastrointestinal tract, where it plays an important role in gut under both physiological and pathological conditions. Although the major effects of cannabinoids in the gut are mediated through effects on enteric neurons, the role of cannabinoids in the enteric nervous system is poorly understood. In the present study, we have used the primary cultures of myenteric ganglia and a newly developed fetal enteric neuronal cell line to identify whether the endocannabinoid, anandamide, affects ganglionic and neuronal survival and the pathways involved. Anandamide had a biphasic effect on ganglionic survival, increasing survival at low concentrations (1nM-0.1uM) and decreasing survival at high concentrations (1-10uM). Maximal survival (68% increase in number of ganglia surviving) occurred at 0.1uM and the ED50 was 3nM. This effect on promoting survival was inhibited by the CB1 antagonist AM251 (1uM) and by AraC (10uM), but not the CB2 antagonist AM630 (1uM). AM630 (1uM) significantly blocked the decreased survival induced by high concentration anandamide (10uM). The enteric glia was involved in anandamide-induced ganglion survival. Anandamide had no effect on the number of neurons/ganglion in the presence of enteric glia, but decreased the number of neurons/ganglion by 15-20% in absence of enteric glia. This effect was partially reversed by CB1 antagonist, AM251 (1uM) (20%-145% at 1nM-10uM) and by CB2 antagonist AM630 (1uM) (40%-185% at 1nM-10uM). In the fetal enteric neural cell line (IM-FEN), anandamide decreased enteric neuronal survival in a concentration-dependent manner at both 39 and 33 degree (11-45% and 10-22%decrease in survival at 1nM-10uM, respectively). Coculture of astrocytes with the enteric neuronal cells was not able to reverse anandamide-mediated neuronal death. Immunocytochemistry and western blot confirmed that the presence of both CB1 and CB2 receptors in enteric neurons (primary cultures and IM-FEN) and glia (primary cultures). In addition, the PLC-beta inhibitor U73122 (1uM) inhibited anandamide induced ganglia survival significantly. Anandamide also induced increased expression of phospho-P44/42MAPK (13-48% at 1nM-10uM) and phospho-AKT (1-28% at 1 nM-10uM) in IM-FEN. We conclude that anandamide has a differential effect on survival of enteric ganglia and neurons. It promotes ganglionic and neuronal survival by CB1 receptors in the presence of glia and this involves the PLC-beta pathway. Conversely, anandamide promotes neuron death in absence of glia as a result of effects on both the MAPK and PI-3K/AKT pathways. Since the endocannabinoid system is upregulated in inflammatory bowel diseases, these effects may play a role in the pathogenesis of the response to inflammation as well as the recovery and reinnervation of the gut following the acute phase of inflammation. The further significance of this work could contribute to developing new therapeutic methods for treatment of inflammatory bowel disease and related symptoms in clinic practice.

Cancer and neurodegeneration are detrimental conditions associated with an inappropriate regulation of cell survival and cell death, causing compromised cells to evade death or excessive death of healthy neurons. The mammalian target of rapamycin complex 2 (mTORC2) has been implicated in the regulation of cell survival by phosphorylating the protein kinase Akt. This is dependent upon the scaffold protein Sin1, a core component of mTORC2. The requirement of Sin1 in cell survival, and in particular in neuronal survival, has not been established due to the early embryonic lethality of mice with a targeted deletion of the Sin1 gene. To circumvent this issue, a novel conditional mouse knockout model was established. The role of Sin1 in regulating cell survival was evaluated in fibroblasts and cortical neurons. The loss of Sin1 significantly affected the phosphorylation and activity of Akt in fibroblasts and caused a reduction in cell survival by potentially inducing premature senescence. In contrast, the loss of Sin1 caused an increase in caspase-independent cell death in cortical neurons. Gene-expression analysis of Sin1 knockout cortical neurons demonstrated an important down-regulation of transcription factors, cytoskeletal proteins and components of signalling pathways involved in neuronal survival, aiding to uncover the mechanism by which Sin1 promotes neuronal survival. Taken together, the results presented in this study show a key role of the scaffold protein Sin1 in regulating neuronal survival.

Implications for the endocannabinoid system in global cerebral ischemia has not been clearly defined. Ischemia produces an excitotoxic environment that is severely damaging to neurons, causing degradation of cell membrane and ultimately cell death. Contradicting research suggests both the benefits and adverse effects of endocannabinoids on neurological injury. Due to the excitotoxic nature of ischemic injury, and the mechanisms at play with endocannabinoid agonists, such as increased transmission of dopamine and glutamate, it is suspected that endocannabinoid antagonists, such as AM251, may a provide cell protection.40 male Wistar rats were separated into 4 groups (n=10/group). The first group of rats were administered AM251 (2 mg/kg, i.p) 30 minutes prior to global cerebral ischemia (four vessel occlusion), while the second group were given AM251, 30 minutes prior to sham surgery. Finally the last two groups were given a vehicle control instead of AM251 and given either ischemia or the sham surgery. Behavioural testing, open field test and elevated plus maze, took place after a five day recovery period following ischemia. Immunohistochemical analyses were performed using to mark tyrosine hydroxylase (TH) and dopamine receptor 1(DRD1) to compare dopamine function amongst groups. Cell survival was also evaluated using thionin staining. Ischemia induced significant reduction in dopamine within the mesolimbic circuit, including: ventral tegmental area, nucleus accumbens, CA3 & CA1 of the hippocampus, and basolateral amygdala. These reductions in dopamine transmission by global ischemia were partially or fully reversed when AM251 was given beforehand. Furthermore, cell survival was increased in the CA1 from treatment of AM251. Behavioural results show similar results that AM251 reversed emotional irregularities associated with ischemia insult. The endocannabinoid antagonist AM251 improves deficits in dopamine function, prevents cell death and regulates emotionality when given prior global cerebral ischemia.

Implications for the endocannabinoid system in global cerebral ischemia has not been clearly defined. Ischemia produces an excitotoxic environment that is severely damaging to neurons, causing degradation of cell membrane and ultimately cell death. Contradicting research suggests both the benefits and adverse effects of endocannabinoids on neurological injury. Due to the excitotoxic nature of ischemic injury, and the mechanisms at play with endocannabinoid agonists, such as increased transmission of dopamine and glutamate, it is suspected that endocannabinoid antagonists, such as AM251, may a provide cell protection.40 male Wistar rats were separated into 4 groups (n=10/group). The first group of rats were administered AM251 (2 mg/kg, i.p) 30 minutes prior to global cerebral ischemia (four vessel occlusion), while the second group were given AM251, 30 minutes prior to sham surgery. Finally the last two groups were given a vehicle control instead of AM251 and given either ischemia or the sham surgery. Behavioural testing, open field test and elevated plus maze, took place after a five day recovery period following ischemia. Immunohistochemical analyses were performed using to mark tyrosine hydroxylase (TH) and dopamine receptor 1(DRD1) to compare dopamine function amongst groups. Cell survival was also evaluated using thionin staining. Ischemia induced significant reduction in dopamine within the mesolimbic circuit, including: ventral tegmental area, nucleus accumbens, CA3 & CA1 of the hippocampus, and basolateral amygdala. These reductions in dopamine transmission by global ischemia were partially or fully reversed when AM251 was given beforehand. Furthermore, cell survival was increased in the CA1 from treatment of AM251. Behavioural results show similar results that AM251 reversed emotional irregularities associated with ischemia insult. The endocannabinoid antagonist AM251 improves deficits in dopamine function, prevents cell death and regulates emotionality when given prior global cerebral ischemia.

No description available.

Neuronal homeostasis is an essential process to protect neurons from over/under-stimulation driven from systematic changes such as synapsis plasticity or tissue damage. Functional stability in neurons relays on the homeostatic plasticity that its disturbance causes irreversible injuries. Hence, a large body of studies elaborated to investigate the underlying mechanism for changes in synaptic connectivity and neuronal function. HIV-1 Tat (Transactivation of transcription), is a well-established neurotoxic protein, released by HIV-1 infected cells in the brain and disturbs neuronal homeostasis. The effects of Tat have been addressed in numerous studies investigating the molecular events associated with neuronal cell survival and death. The emergence of lncRNAs as critical players in disease etiology placed them in the spotlight to study pathogenesis of human diseases. Due to its capacity to modulate host transcriptome, HIV-1 Tat protein has been subjected to increasing genome-wide examinations. This study showed that exposing primary rat neurons to Tat resulted in the up-regulation of an uncharacterized long-non-coding RNA (lncRNA), LOC102549805 (lncRNA-U1). Evidence exists that increased expression of lncRNA-U1 in neurons disrupts bioenergetic pathways by dysregulating homeostasis of Ca2+, mitigating mitochondrial oxygen reduction, and decreasing ATP production leading to mitochondrial impairment in neurons. These changes were associated with imbalances in autophagy and apoptosis pathways via the Tat-mediated lncRNA-U1 induction. Additionally, this study showed the ability of Tat to modulate the expression of the neuropeptide B/W receptor 1 (NPBWR1) gene via the up-regulation of lncRNA-U1. Collectively, my results identified the Tat-mediated lncRNA-U1 elevation disturbs neuronal homeostasis. Our observations of lncRNA-U1 knock-down experiments indicated the novel lncRNA LOC102549805 (U1) as a viable therapeutic target to prevent HIV-1 Tat neurotoxicity. / Biology

Kainic acid induced excitotoxicity causes pyramidal cell death in the CA3a/b region of the hippocampus. Electrical synapses, gap junctional communication, and single membrane channels in non-junctional membranes (hemichannels) composed of connexin36 (Cx36) have been implicated in both seizure propagation and the spread of excitotoxic cell death. In rats, Cx36 protein is expressed by pyramidal neurons. Localization of protein in mouse, however, is highly controversial. Expression is reported to be restricted to hippocampal interneurons yet the same excitotoxic mechanisms (electrical and metabolic coupling between pyramidal neurons) are invoked to explain the role of Cx36 in excitotoxic pyramidal loss in murine brain. To address this controversy, I show by confocal immunofluorescence and in situ hybridization that Cx36 protein expression is restricted to interneurons and microglia in murine hippocampus and is not expressed by, or is below level of detection in pyramidal neurons. Using behavioural and electrophysiological measures, seizure propagation was found to be moderately enhanced in the absence of Cx36 likely due to the loss of interneuron-mediated synchronous inhibition of the pyramidal cells. Further, CA3a/b neurons die post kainic acid injury in the presence of Cx36 but are protected in Cx36-/- mice. When delayed excitotoxic cell death is maximal, Cx36 is primarily expressed by activated microglia as demonstrated by confocal immunofluorescence, in situ hybridization, and Western blotting. These activated microglia are located in the direct vicinity of, and surrounding cells in the damaged Ca3a/b region. Finally, I show that loss of Cx36 from activated microglia in mice is sufficient to prevent excitotoxic cell death in the CA3a/b with surviving neurons functional as assessed by both electrophysiological and behavioural measures. Together, these data identify a new mechanism of excitotoxic injury, mediated by neuronal-glial interactions, and dependent on microglial Cx36 expression.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2004. / Title from first page of PDF document. Includes bibliographical references (p. 36-47).

Made available in DSpace on 2014-12-17T15:28:52Z (GMT). No. of bitstreams: 1 ThemisTSS_DISSERT.pdf: 1249174 bytes, checksum: 23a39272c35586e8f475b1aa239af353 (MD5) Previous issue date: 2012-12-21 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The cortical development requires a precise process of proliferation, migration, survival and differentiation of newly formed neurons to finally achieve the development of a functional network. Different kinases, such as PKA, CaMKII, MAPK and PI3K, phosphorylate the transcription factors CREB, and thus activate it, inducing CREB-dependent gene expression. In order to identify the involvement of such signaling pathways mediated by CREB over neuronal differentiation and survival, in vitro experiments of cell culture were conducted using pharmacological kinase inhibitors and genetic techniques to express different forms of CREB (A-CREB and CREB-FY) in cortical neurons. Inhibition of PKA and CaMKII decreased the length of neuronal processes (neurites); whereas inhibition of MAPK did not affect the length, but increased the number of neurites. Blockade of PI3K do not appear to alter neuronal morphology, nor the soma size changed with the kinase blockades. CREB activation (CREB-FY) along with MAPK and PI3K blockades presented a negative side effect over neuritic growth and the expression of A-CREB leaded to a significant decrease in neuronal survival after 60h in vitro and mimicked some of the effects on neuronal morphology observed with PKA and CaMKII blockade. In summary the signaling through CREB influences the morphology of cortical neurons, particularly when phosphorylated by PKA, and CREB signaling is also important for survival of immature neurons prior to the establishment of fully functional synaptic contacts. Our data contribute to understanding the role of CREB signaling, activated by different routes, on survival and neuronal differentiation and may be valuable in the development of regenerative strategies in different neurological diseases / O desenvolvimento cortical requer um minucioso processo de prolifera??o, migra??o, sobreviv?ncia e diferencia??o celular para que se possa alcan?ar a elabora??o de uma rede neuronal funcional. Diferentes kinases, tais quais a PKA, CaMKII, MAPK e PI3K, fosforilam o fator de transcri??o CREB, ativando-o, e induzindo em ultima inst?ncia a express?o de genes CREB-dependentes. A fim de identificar o envolvimento de tais vias de sinaliza??o mediadas por CREB sobre a diferencia??o e sobreviv?ncia neuronal, experimentos in vitro de cultura celular foram conduzidos fazendo-se uso de f?rmacos bloqueadores das kinases e de t?cnicas gen?ticas para expressar diferentes formas do CREB (A-CREB e CREB-FY) em neur?nios corticais. A inibi??o da PKA e da CAMKII diminuiu o comprimento dos neuritos; enquanto a inibi??o da MAPK n?o afetou o comprimento, mas aumentou o numero de neuritos. O bloqueio da PI3K n?o pareceu alterar a morfologia neuronal, nem o tamanho do soma foi afetado pelo bloqueio dessas kinases. A ativa??o de CREB (CREB-FY) na presen?a de bloqueadores da MAPK e PI3K teve um efeito negativo sobre o crescimento neur?tico e a express?o do A-CREB provocou uma redu??o significativa da sobreviv?ncia neuronal a partir de 60h in vitro e revelou similaridades quanto ? morfologia neuronal observadas com o bloqueio da PKA e CaMKII. Em suma, a sinaliza??o mediada por CREB influi na morfologia de neur?nios corticais, principalmente quando fosforilado pela PKA, e o bloqueio da sinaliza??o via CREB interfere na sobreviv?ncia neuronal mesmo antes do aparecimento de atividade sin?ptica. Nossos resultados contribuem para o entendimento da sinaliza??o por CREB, ativado por diferentes vias, sobre a sobreviv?ncia e diferencia??o neuronal, podendo ser de grande valia na elabora??o de estrat?gias regenerativas em diferentes doen?as neurol?gicas