Alzheimer disease (AD) is characterized by a progressive loss of cognitive functions due to specific neurodegeneration and death of basal forebrain cholinergic neurons (BFCN). BFCNs innervate cortical and hippocampal areas and retrogradely transport NGF, which sustains their survival and differentiation. An impairment in NGF production and/or transport is considered to be one of the factors involved in neurodegeneration in AD. NGF retrograde transport is mediated by neurotrophin receptors (NTRs) so an imbalance in their expression could drive neurodegeneration. The goal of our study was to test whether exogenous neurotrophins alter the expression of NTRs and cholinergic markers on BFCN. To address this question we set up in vitro cultured BFCNs. We found that our cultures expressed mRNA and protein of NTRs (p75-NTR, TrkA, TrkB, TrkC) and cholinergic markers (ChAT and CHT). By using immunofluorescence, we observed complete p75-NTR, and partial TrkA, neuronal colocalization with cholinergic markers. We found that NGF (100ng/ml) induced a significant and BFCN-specific increase of the number of ChAT and p75-NTR positive neurons. BDNF (100ng/ml) and KCl (25mM) induced a significant increase of the number of p75-NTR positive neurons due to higher expression levels in GABAergic neurons. NGF and KCl also induced significant BFCN-specific increase of p75-NTR protein expression and fluorescence signal spreading along neuronal processes due to neurite outgrowth or to signal spreading in existing neurites. In conclusion, we developed and validated an in vitro model of cholinergic neurons. Specifically, both NTs and KCl induced p75 NTR expression in BFCN, suggesting that this NTR may undergo significant changes after trophic and activity-dependent stimulations.
Modulation of NTRs expression and of cholinergic function in in vitro rat BFCNs
DALFINI, Anna;FORMAGGIO, Elena;CHIAMULERA, Cristiano;FUMAGALLI, Guido Francesco
2007-01-01
Abstract
Alzheimer disease (AD) is characterized by a progressive loss of cognitive functions due to specific neurodegeneration and death of basal forebrain cholinergic neurons (BFCN). BFCNs innervate cortical and hippocampal areas and retrogradely transport NGF, which sustains their survival and differentiation. An impairment in NGF production and/or transport is considered to be one of the factors involved in neurodegeneration in AD. NGF retrograde transport is mediated by neurotrophin receptors (NTRs) so an imbalance in their expression could drive neurodegeneration. The goal of our study was to test whether exogenous neurotrophins alter the expression of NTRs and cholinergic markers on BFCN. To address this question we set up in vitro cultured BFCNs. We found that our cultures expressed mRNA and protein of NTRs (p75-NTR, TrkA, TrkB, TrkC) and cholinergic markers (ChAT and CHT). By using immunofluorescence, we observed complete p75-NTR, and partial TrkA, neuronal colocalization with cholinergic markers. We found that NGF (100ng/ml) induced a significant and BFCN-specific increase of the number of ChAT and p75-NTR positive neurons. BDNF (100ng/ml) and KCl (25mM) induced a significant increase of the number of p75-NTR positive neurons due to higher expression levels in GABAergic neurons. NGF and KCl also induced significant BFCN-specific increase of p75-NTR protein expression and fluorescence signal spreading along neuronal processes due to neurite outgrowth or to signal spreading in existing neurites. In conclusion, we developed and validated an in vitro model of cholinergic neurons. Specifically, both NTs and KCl induced p75 NTR expression in BFCN, suggesting that this NTR may undergo significant changes after trophic and activity-dependent stimulations.
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