Regulated lentiviral NGF gene transfer controls rescue of medial septal cholinergic neurons.
ABSTRACT Nerve growth factor (NGF) has been shown to promote survival and function of cholinergic neurons in the basal forebrain in various models of neuronal degeneration in rodents and primates. We examined whether a regulatable in vivo expression system can control the survival of cholinergic neurons after injury, using a tetracycline-regulated promoter ("tet-off" system) to modulate lentiviral NGF gene delivery. Two weeks after lesions to cholinergic neurons, significant cell rescue (65+/-8% neuron survival; P<0.005 compared to controls) was observed when NGF expression was activated. Treatment with the tetracycline analog doxycycline to turn gene expression "off" resulted in a significant loss of cholinergic neurons (only 37+/-5% neurons remained, an amount that did not differ from untreated, lesioned controls). Animals treated with a constitutively active and robust nonregulated NGF expression system showed the same degree of neuronal rescue (73+/-8%) as animals treated with activated tet-regulated vectors. ELISA measurements confirmed that oral treatment of animals with doxycycline reduced NGF protein levels to levels in untreated control subjects. These data demonstrate for the first time that NGF delivery by lentiviral gene transfer using tetracycline-regulated promoters can completely regulate neuronal rescue and protein production in the brain.
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ABSTRACT: Two major neurotrophic factors, NGF and BDNF are involved in a number of physiological processes associated with neuronal growth, survival and plasticity. There are an increasing number of papers demonstrating their ability to serve as neuroprotective molecules under various pathological conditions. At the same time, it remains unclear whether both NGF and BDNF have similar roles under pathological conditions and their effects on the electrophysiological properties of neurons after acute pathogen exposure. In the present paper we investigated the neuroprotective role of these two neurotrophins in a well-characterized model of Aβ-dependent impairment of LTP. Using lentiviral gene delivery we performed long-term elevation of neurotrophin expression in the dentate gyrus of rats. One week after virus injection acute brain slices were incubated with beta-amyloid (25-35) for 1 hour and afterwards in vitro LTP induction was performed in medial perforant path - dentate gyrus synapses. We demonstrate that chronic elevation of NGF but not BDNF concentration protects LTP induction from beta-amyloid action. Further inhibitory analysis suggests that the effect of nerve growth factor is mediated by PI3K-signaling cascade. Copyright © 2015. Published by Elsevier Ltd.Neuroscience 01/2015; 289. DOI:10.1016/j.neuroscience.2014.12.063 · 3.33 Impact Factor
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ABSTRACT: Dysfunction of growth factor (GF) activities contributes to the decline and death of neurons during aging and in neurodegenerative diseases. In addition, neurons become more resistant to GF signaling with age. Micro (mi)RNAs are posttranscriptional regulators of gene expression that may be crucial to age- and disease-related changes in GF functions. MiR-126 is involved in regulating insulin/IGF-1/phosphatidylinositol-3-kinase (PI3K)/AKT and extracellular signal-regulated kinase (ERK) signaling, and we recently demonstrated a functional role of miR-126 in dopamine neuronal cell survival in models of Parkinson's disease (PD)-associated toxicity. Here, we show that elevated levels of miR-126 increase neuronal vulnerability to ubiquitous toxicity mediated by staurosporine (STS) or Alzheimer's disease (AD)-associated amyloid beta 1-42 peptides (Aβ1-42). The neuroprotective factors IGF-1, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and soluble amyloid precursor protein α (sAPPα) could diminish but not abrogate the toxic effects of miR-126. In miR-126 overexpressing neurons derived from Tg6799 familial AD model mice, we observed an increase in Aβ1-42 toxicity, but surprisingly, both Aβ1-42 and miR-126 promoted neurite sprouting. Pathway analysis revealed that miR-126 overexpression downregulated elements in the GF/PI3K/AKT and ERK signaling cascades, including AKT, GSK-3β, ERK, their phosphorylation, and the miR-126 targets IRS-1 and PIK3R2. Finally, inhibition of miR-126 was neuroprotective against both STS and Aβ1-42 toxicity. Our data provide evidence for a novel mechanism of regulating GF/PI3K signaling in neurons by miR-126 and suggest that miR-126 may be an important mechanistic link between metabolic dysfunction and neurotoxicity in general, during aging, and in the pathogenesis of specific neurological disorders, including PD and AD.Molecular Neurobiology 11/2014; DOI:10.1007/s12035-014-8989-x · 5.29 Impact Factor