Calcineurin contributes to the enhancing effect of adenosine on nerve growth factor-induced neurite outgrowth via the decreased duration of p38 mitogen-activated protein kinase phosphorylation.
ABSTRACT Adenosine enhances nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells. We found that adenosine increases NGF-induced phosphorylation of extracellular signal-regulated kinase (ERK), but decreases the duration of phosphorylation of p38 mitogen-activated protein (MAP) kinase. Therefore, we further examined the involvement of protein phosphatase in these effects of adenosine. FK506, a specific calcineurin inhibitor, inhibited the enhancing effect of adenosine on the NGF-induced neurite outgrowth and increased the duration of p38 MAP kinase phosphorylation without affecting ERK phosphorylation. These results suggest that adenosine decreases the duration of p38 MAP kinase via calcineurin activation, which contributes to the enhancement of NGF-induced neurite outgrowth.
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ABSTRACT: Environmental enrichment (EE) has marked beneficial effects on cognitive capacity. Given the possibility that this form of neuronal plasticity could function via the actuation of the same cellular signaling pathways that underlie learning/memory formation, we examined whether the MAPK cascade effector, mitogen/stress-activated kinase 1 (MSK1), could play a role in this process. MSK1 functions as a key signaling intermediate that couples changes in neuronal activity into inducible gene expression, neuronal plasticity, and learning/memory. Here, we show that MSK1 is expressed in excitatory cell layers of the hippocampus, progenitor cells of the subgranular zone (SGZ), and adult-born immature neurons. MSK1(-/-) mice exhibit reduced spinogenesis and decreased dendritic branching complexity in hippocampal neurons, compared with WT mice. Further, in MSK1(-/-) mice, progenitor cell proliferation within the SGZ was significantly reduced and, correspondingly, the number of immature neurons within the dentate gyrus was significantly reduced. Consistent with prior work, MSK1(-/-) mice displayed deficits in both spatial and recognition memory tasks. Strikingly, cognitive enhancement resulting from a 40-d period of EE was markedly reduced in MSK1(-/-) animals. MSK1(-/-) mice exhibited reduced levels of EE-induced spinogenesis and SGZ progenitor proliferation. Taken together, these data reveal that MSK1 serves as a critical regulator of hippocampal physiology and function and that MSK1 serves as a key conduit by which enriching stimuli augment cellular plasticity and cognition.Learning & memory (Cold Spring Harbor, N.Y.) 10/2012; 19(11):550-60. DOI:10.1101/lm.025775.112
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ABSTRACT: Development of the nervous system is a complex process, involving coordinated regulation of diverse cellular processes including proliferation, differentiation and synaptogenesis. Disturbances to brain development such as pre- and perinatal hypoxia have been linked to behavioural and late onset of neurological disorders. This study examines the effect of hypoxia on neurite outgrowth in PC12 cells. Hypoxia not only caused a rapid induction of neurite outgrowth, but also synergistically enhanced nerve growth factor (NGF)-induced neurite outgrowth up to 24 h. Transactivation of TrkA receptors was ruled out since the TrkA inhibitor K252a did not block hypoxia-induced neurite outgrowth. Adenosine deaminase prevented hypoxia-induced neurite outgrowth indicating that the effect is mediated by adenosine. Use of the specific adenosine A2A receptor agonist CGS21680 and antagonist 8-3(chlorostyryl)caffeine demonstrated that activation of this receptor is critical for hypoxia-induced neurite outgrowth. Hypoxia-induced neurite outgrowth was blocked by the adenylate cyclase inhibitor, MDL-12,330A, indicating a role for activation of this enzyme in the pathway. Hypoxia was further shown to cause a decrease in growth-associated protein (GAP)-43 levels and a lack of induction of betaIII tubulin, in contrast to NGF treatment which resulted in increased cellular levels of both of these proteins. These findings suggest that hypoxia induces neurite outgrowth in PC12 cells via a pathway distinct from that activated by NGF. Thus, exposure to hypoxia at critical stages of development may contribute to aberrant neurite outgrowth and could be a factor in the pathogenesis of certain delayed developmental neurological disorders.Neuroscience 02/2005; 131(2):321-9. DOI:10.1016/j.neuroscience.2004.11.015
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ABSTRACT: Neurodegenerative brain disorders such as Alzheimer's disease (AD) have been well investigated. However, significant methods for the treatment of the promotion and progression of AD are unavailable to date. Recent studies suggested that the redox imbalance and the accumulation of amyloid-beta (Abeta) peptide occurring in the brain of AD patients lead to oxidatively-induced apoptotic cell death. Here, we show the effects of Shengmai-san (SMS) on Abeta-induced cytotoxicity in PC-12 cells. SMS dose-dependently attenuated the cytotoxicity by Abeta incubation and also prevented the morphological damage in neurites of the PC-12 cells. Hemeoxygenase-1 and glutathione peroxidase-1 expressions were increased by SMS pretreatment. SMS decreased the phosphorylation level of c-jun amino-terminal kinase (JNK) and the activity of caspase-3, which were enhanced by Abeta incubation. Of importance, SMS treatment promoted neurite outgrowth. These data demonstrated dual roles of SMS in PC-12 cells. SMS prevents the apoptosis through the enhancement of anti-oxidant enzymes and inhibition of the JNK signaling pathway with the promotion of nerve cell maturation, thus suggesting benefits of SMS for the treating of neurodegenerative diseases. It may also be beneficial not only for the treatment of brain disorders but also for other diseases caused by oxidative stress.Journal of Pharmacological Sciences 06/2007; 104(1):73-81.