Neurotrophic Factor BDNF, Physiological Functions and Therapeutic Potential in Depression, Neurodegeneration and Brain Cancer

Brain-derived neurotrophic factor (BDNF) is one of the most distributed and extensively studied neurotrophins in the mammalian brain. BDNF signals through the tropomycin receptor kinase B (TrkB) and the low affinity p75 neurotrophin receptor (p75NTR). BDNF plays an important role in proper growth, development, and plasticity of glutamatergic and GABAergic synapses and through modulation of neuronal differentiation, it influences serotonergic and dopaminergic neurotransmission. BDNF acts as paracrine and autocrine factor, on both pre-synaptic and post-synaptic target sites. It is crucial in the transformation of synaptic activity into long-term synaptic memories. BDNF is considered an instructive mediator of functional and structural plasticity in the central nervous system (CNS), influencing dendritic spines and, at least in the hippocampus, the adult neurogenesis. Changes in the rate of adult neurogenesis and in spine density can influence several forms of learning and memory and can contribute to depression-like behaviors. The possible roles of BDNF in neuronal plasticity highlighted in this review focus on the effect of antidepressant therapies on BDNF-mediated plasticity. Moreover, we will review data that illustrate the role of BDNF as a potent protective factor that is able to confer protection against neurodegeneration, in particular in Alzheimer’s disease. Finally, we will give evidence of how the involvement of BDNF in the pathogenesis of brain glioblastoma has emerged, thus opening new avenues for the treatment of this deadly cancer

Neurotrophic Factor BDNF, Physiological Functions and Therapeutic Potential in Depression, Neurodegeneration and Brain Cancer

Brain-derived neurotrophic factor (BDNF) is one of the most distributed and extensively studied neurotrophins in the mammalian brain. BDNF signals through the tropomycin receptor kinase B (TrkB) and the low affinity p75 neurotrophin receptor (p75NTR). BDNF plays an important role in proper growth, development, and plasticity of glutamatergic and GABAergic synapses and through modulation of neuronal differentiation, it influences serotonergic and dopaminergic neurotransmission. BDNF acts as paracrine and autocrine factor, on both pre-synaptic and post-synaptic target sites. It is crucial in the transformation of synaptic activity into long-term synaptic memories. BDNF is considered an instructive mediator of functional and structural plasticity in the central nervous system (CNS), influencing dendritic spines and, at least in the hippocampus, the adult neurogenesis. Changes in the rate of adult neurogenesis and in spine density can influence several forms of learning and memory and can contribute to depression-like behaviors. The possible roles of BDNF in neuronal plasticity highlighted in this review focus on the effect of antidepressant therapies on BDNF-mediated plasticity. Moreover, we will review data that illustrate the role of BDNF as a potent protective factor that is able to confer protection against neurodegeneration, in particular in Alzheimer’s disease. Finally, we will give evidence of how the involvement of BDNF in the pathogenesis of brain glioblastoma has emerged, thus opening new avenues for the treatment of this deadly cancer

Generation of High-Yield, Functional Oligodendrocytes from a c-myc Immortalized Neural Cell Line, Endowed with Staminal Properties

Neural stem cells represent a powerful tool to study molecules involved in pathophysiology of Nervous System and to discover new drugs. Although they can be cultured and expanded in vitro as a primary culture, their use is hampered by their heterogeneity and by the cost and time needed for their preparation. Here we report that mes-c-myc A1 cells (A1), a neural cell line, is endowed with staminal properties. Undifferentiated/proliferating and differentiated/non-proliferating A1 cells are able to generate neurospheres (Ns) in which gene expression parallels the original differentiation status. In fact, Ns derived from undifferentiated A1 cells express higher levels of Nestin, Kruppel-like factor 4 (Klf4) and glial fibrillary protein (GFAP), markers of stemness, while those obtained from differentiated A1 cells show higher levels of the neuronal marker beta III tubulin. Interestingly, Ns differentiation, by Epidermal Growth Factors (EGF) and Fibroblast Growth Factor 2 (bFGF) withdrawal, generates oligodendrocytes at high-yield as shown by the expression of markers, Galactosylceramidase (Gal-C) Neuron-Glial antigen 2 (NG2), Receptor-Interacting Protein (RIP) and Myelin Basic Protein (MBP). Finally, upon co-culture, Ns-A1-derived oligodendrocytes cause a redistribution of contactin-associated protein (Caspr/paranodin) protein on neuronal cells, as primary oligodendrocytes cultures, suggesting that they are able to form compact myelin. Thus, Ns-A1-derived oligodendrocytes may represent a time-saving and low-cost tool to study the pathophysiology of oligodendrocytes and to test new drugs

In A1 cells, E₂ induce ERK1/2 phosphorylation according to the proliferative/differentiation status.

<p>Western blot detection of p-ERK1/2 and ERK1/2 proteins in proliferating/undifferentiated (A) and non-prolifearting/differentiated A1 cells (C) treated at indicated time with 10 nM of E₂ and 10 mM of ICI 182–780. Two specific bands were observed respectively at 44 and 42 kDa. Each blot is representative of three separate experiments. The diagrams show the relative quantitation of p-ERK1/2 and ERK1/2 in proliferating (B) and non-proliferating (D) A1 cells. Data are expressed as ratios of p-ERK1-2/ERK1-2. In diagrams are also showed the different trend lines of the kinetic of p-ERK following E₂ stimulation. Asterisks represent p<0.01 when compared to control cultures treated with vehicle (ANOVA, Scheffè F-test).</p

E₂–dependent survival is affected by Cav1 downregulation.

<p>The diagrams show the E₂ effect, assessed by MTT assay, in non-proliferating A1 (A) and mesPC (B) cells after transfection of non-targeting, NT, or Cav1 siRNA construct (siCav). P0 indicates the start point of E₂ stimulation (5DIV). Asterisks represent p<0.01 when compared to control cultures treated with vehicle (ANOVA, Scheffè F-test). The hash sign represents p<0.05 between control cultures at 7DIV compared to control cultures at 5DIV (ANOVA, Scheffè F-test).</p

In A1 cells and in mesPC, differentiation increases Cav1 protein expression but not ERα.

<p>Lysates from A1 and from mesPC proliferating/undifferentiated and non-proliferating/differentiated were immunoblotted using ERα (A), Cav1 (B) and ß-actin (A, C) antibodies. ERα, Cav1 and ß-actin specific bands were detected at 67 kDa, 21 kDa and 42 kDa in both proliferating (prol.) and non-proliferating (diff.) cells. (B, D) The diagrams show the relative quantitation of the ERα and Cav1 in proliferating and non-proliferating A1 and in mesPC cell line respectively. Data are expressed as ratios of ERα/ß-actin and Cav1/ß–actin. The blots are representative of three separate experiments. Asterisks represent p<0.01 when compared to proliferating cultures (ANOVA, Scheffè F-test).</p

In A1 cells the different kinetics of p-ERK1/2 activation are abolished by β-cyclodextrin administration.

<p>Western blot detection of p-ERK1/2 and ERK1/2 proteins in proliferating (A) and non-proliferating A1 cells (C) treated at indicated time with E₂ and ß-cyclodextrin. Two specific bands were observed respectively at 44 and 42 kDa. Each blot is representative of three separate experiments. The diagrams show the relative quantization of p-ERK1/2 and ERK1/2 in proliferating (B) and non-proliferating (D) A1 cells. Data are expressed as ratios of p-ERK1-2/ERK1-2. The trend line shows the kinetic of p-ERK1/2 following E₂ stimulation. Asterisks represent p<0.01 when compared to control cultures treated with vehicle (ANOVA, Scheffè F-test).</p

In mesPC, E₂ induces ERK1/2 phosphorylation according to the proliferative/differentiation status.

<p>Western blot detection of p-ERK1/2 and ERK1/2 proteins in proliferating (A) and non-proliferating mesPC (C) treated at indicated time with 10 nM of E₂ and 10 mM of ICI 182–780. Two specific bands were observed respectively at 44 and 42 kDa. Each blot is representative of three separate experiments. The diagrams show the relative quantization of p-ERK1/2 and ERK1/2 in proliferating (B) and non-proliferating primary cells (D). Data are expressed as ratios of p-ERK1-2/ERK1-2. In diagrams are also showed the different trend lines of the kinetic of p-ERK1/2 following E₂ stimulation. Asterisks represent p<0.01 when compared to control cultures treated with vehicle (ANOVA, Scheffè F-test).</p