Tyrosine hydroxylase induction by basic fibroblast growth factor and cyclic AMP analogs in striatal neural stem cells: role of ERK1/ERK2 mitogen-activated protein kinase and protein kinase C

Generation of GABAergic striatal neurons by a novel iPSC differentiation protocol enabling scalability and cryopreservation of progenitor cells

Cell models are promising tools for studying hereditary human neurodegenerative diseases. Neuronal derivatives of pluripotent stem cells provide the opportunity to investigate different stages of the neurodegeneration process. Therefore, easy and large-scale production of relevant cell types is a crucial barrier to overcome. In this work, we present an alternative protocol for iPSC differentiation into GABAergic medium spiny neurons (MSNs). The first stage involved dual-SMAD signalling inhibition through treatment with SB431542 and LDN193189, which results in the generation of neuroectodermal cells. Moreover, we used bFGF as a neuronal survival factor and dorsomorphin to inhibit BMP signalling. The combined treatment of dorsomorphin and SB431542 significantly enhanced neuronal induction, which was confirmed by the increased expression of the telencephalic-specific markers SOX1 and OTX2 as well as the forebrain marker PAX6. The next stage involved the derivation of actively proliferating MSN progenitor cells. An important feature of our protocol at this stage is the ability to perform prolonged cultivation of precursor cells at a high density without losing phenotypic properties. Moreover, the protocol enables multiple expansion steps (> 180 days cultivation) and cryopreservation of MSN progenitors. Therefore, this method allows quick production of a large number of neurons that are relevant for basic research, large-scale drug screening, and toxicological studies.

A High-fat Diet Induces a Loss of Midbrain Dopaminergic Neuronal Function That Underlies Motor Abnormalities

Movement defects in obesity are associated with peripheral muscle defects, arthritis, and dysfunction of motor control by the brain. Although movement functionality is negatively correlated with obesity, the brain regions and downstream signaling pathways associated with movement defects in obesity are unclear. A dopaminergic neuronal pathway from the substantia nigra (SN) to the striatum is responsible for regulating grip strength and motor initiation through tyrosine hydroxylase (TH) activity-dependent dopamine release. We found that mice fed a high-fat diet exhibited decreased movement in open-field tests and an increase in missteps in a vertical grid test compared with normally fed mice. This motor abnormality was associated with a significant reduction of TH in the SN and striatum. We further found that phosphorylation of c-Jun N-terminal kinase (JNK), which modulates TH expression in the SN and striatum, was decreased under excess-energy conditions. Our findings suggest that high calorie intake impairs motor function through JNK-dependent dysregulation of TH in the SN and striatum.

Directional induction of dopaminergic neurons from neural stem cells using substantia nigra homogenates and basic fibroblast growth factor

To date, complex components of available reagents have been used for directional induction of neural stem cells into dopaminergic neurons, resulting in a poor ability to repeat experiments. This study sought to investigate whether a homogenate of the substantia nigra of adult rats and/or basic fibroblast growth factor could directionally induce neural stem cells derived from the subventricular zone of embryonic rats to differentiate into dopaminergic neurons. Tyrosine hydroxylase-positive cells were observed exclusively after induction with the homogenate supernatant of the substantia nigra from adult rats and basic fibroblast growth factor for 48 hours in vitro. However, in the groups treated with homogenate supernatant or basic fibroblast growth factor alone, tyrosine hydroxylase expression was not observed. Moreover, the content of dopamine in the culture medium of subventricular zone neurons was significantly increased at 48 hours after induction with the homogenate supernatant of the substantia nigra from adult rats and basic fibroblast growth factor. Experimental findings indicate that the homogenate supernatant of the substantia nigra from adult rats and basic fibroblast growth factor could directionally induce neural stem cells derived from the subventricular zone of embryonic rats to differentiate into dopaminergic neurons in the substantia nigra with the ability to secrete dopamine.

Cholecystokinin-8 induces brain-derived neurotrophic factor expression in noradrenergic neuronal cells

The sulfated cholecystokinin octapeptide (CCK-8S) is one of the most abundant CCK fragment in the brain, but the effects of CCK-8S on locus coeruleus (LC) noradrenergic (NA) neuronal cells activity have not been studied. In this study, we investigated the effects of CCK-8S on the expression of brain-derived neurotrophic factor (BDNF) in LC NA neuronal cell line, LC3541. Results showed that CCK-8S (10 nM) elevates BDNF levels time-dependently and by 1.82-fold after 4h of incubation. In addition, pretreatment with CCK-8S reversed H₂O₂ (100 μM)-mediated down-regulation of BDNF expression, and effectively suppressed H₂O₂-induced caspase-3 activation. Furthermore, CCK-8S markedly induced expression of neuronal survival markers, such as extracellular signal-regulated kinase 1/2 (ERK 1/2), Akt/protein kinase B (PKB), Bcl-2, and peroxisome proliferators-activated receptor gamma coactivator-1α (PGC-1α). Pharmacological inhibitors of ERK 1/2, Akt/PKB, and protein kinase A (PKA) reversed CCK-8S-mediated BDNF induction in LC3541 cells. These results suggest the first evidence that CCK-8S can protect noradrenergic neurons and enhance the expression of BDNF via ERK 1/2-Akt/PKB-PKA-dependent pathways.

Neural stem/progenitor cells from the adult human spinal cord are multipotent and self-renewing and differentiate after transplantation

Neural stem/progenitor cell (NSPC) transplantation is a promising therapy for spinal cord injury (SCI). However, little is known about NSPC from the adult human spinal cord as a donor source. We demonstrate for the first time that multipotent and self-renewing NSPC can be cultured, passaged and transplanted from the adult human spinal cord of organ transplant donors. Adult human spinal cord NSPC require an adherent substrate for selection and expansion in EGF (epidermal growth factor) and FGF2 (fibroblast growth factor) enriched medium. NSPC as an adherent monolayer can be passaged for at least 9 months and form neurospheres when plated in suspension culture. In EGF/FGF2 culture, NSPC proliferate and primarily express nestin and Sox2, and low levels of markers for differentiating cells. Leukemia inhibitory factor (LIF) promotes NSPC proliferation and significantly enhances GFAP expression in hypoxia. In differentiating conditions in the presence of serum, these NSPC show multipotentiality, expressing markers of neurons, astrocytes, and oligodendrocytes. Dibutyryl cyclic AMP (dbcAMP) significantly enhances neuronal differentiation. We transplanted the multipotent NSPC into SCI rats and show that the xenografts survive, are post-mitotic, and retain the capacity to differentiate into neurons and glia.

Together, these findings reveal that multipotent self-renewing NSPC cultured and passaged from adult human spinal cords of organ transplant donors, respond to exogenous factors that promote selective differentiation, and survive and differentiate after transplantation into the injured spinal cord.

Physicochemical control of adult stem cell differentiation: shedding light on potential molecular mechanisms

Realization of the exciting potential for stem-cell-based biomedical and therapeutic applications, including tissue engineering, requires an understanding of the cell-cell and cell-environment interactions. To this end, recent efforts have been focused on the manipulation of adult stem cell differentiation using inductive soluble factors, designing suitable mechanical environments, and applying noninvasive physical forces. Although each of these different approaches has been successfully applied to regulate stem cell differentiation, it would be of great interest and importance to integrate and optimally combine a few or all of the physicochemical differentiation cues to induce synergistic stem cell differentiation. Furthermore, elucidation of molecular mechanisms that mediate the effects of multiple differentiation cues will enable the researcher to better manipulate stem cell behavior and response.

Neural stem/progenitor cells differentiate in vitro to neurons by the combined action of dibutyryl cAMP and interferon-gamma

Transplantation of neural stem/progenitor cells (NSPCs) is a promising strategy for repair of the diseased/injured central nervous system (CNS); however, controlling their differentiation remains a significant hurdle. This study is aimed at controlling differentiation and specifically at screening exogenous factors to direct NSPC differentiation into neurons in vitro. In this study, adult rat SVZ-derived NSPCs were treated with several factors and screened individually and in combination for changes in cellular morphology, neuronal marker expression, quantitative real-time qRT-PCR, and electrophysiological properties. These in vitro screens showed that of all the different treatments, dibutyryl cyclic AMP (dbcAMP) and interferon-gamma (IFN-gamma) enhanced neuronal differentiation most significantly compared to the 1% fetal bovine serum (FBS) controls. Importantly, the combined treatment of NSPCs with dbcAMP and IFN-gamma promoted greater neuronal differentiation as reflected by an increase in beta-III tubulin expression and morphological differentiation. Interestingly, the neurons that were generated from the NSPCs in vitro in the presence of dbcAMP and IFN-gamma, alone or in combination, responded to exogenous glutamate (Glu), but not gamma-aminobutyric acid (GABA), indicating that these neurons express glutamate receptors. These NSPC-derived neurons may be promising for neural regenerative strategies in the CNS.

Mobilization of neural stem cells and generation of new neurons in 6-OHDA-lesioned rats by intracerebroventricular infusion of liver growth factor

Neural stem cells with self-renewal and multilineage potential persist in the subventricular zone of the adult mammalian forebrain. These cells remain relatively quiescent but, under certain conditions, can be stimulated, giving rise to new neurons. Liver growth factor (LGF) is a mitogen for liver cells that shows biological activity in extrahepatic sites and is useful for neuroregenerative therapies. The aim of this study was to investigate the potential neurogenic activity of LGF in the 6-hydroxydopamine rat model of Parkinson's disease. Proliferation was significantly increased in the subventricular zone and denervated striatum of rats receiving ICV LGF infusions, and 25% of the proliferating cells were doublecortin-positive neurons. Doublecortin-positive cells with the morphology of migrating neuroblasts were also observed in the dorsal and ventral regions of the striatum of LGF-infused animals. Moreover, some newly generated cells were neuronal nuclei-positive mature neurons. LGF also stimulated microglia and induced astrogliosis, both phenomena associated with generation and migration of new neurons in the adult brain. In summary, our study shows that LGF stimulates neurogenesis when applied intraventricularly in 6-hydroxydopamine-lesioned rats. Considering that this factor also promotes neuronal migration into damaged tissue, we propose LGF as a novel factor useful for neuronal replacement in neurodegenerative diseases.

Modulation of tyrosine hydroxylase expression by melatonin in human SH-SY5Y neuroblastoma cells

We have previously reported in vivo preservation of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine synthesis, following treatment with physiological doses of melatonin, in a 6-hydroxydopamine model of Parkinson's disease. Based on these findings, we postulated that melatonin would similarly modulate the expression of TH in vitro. Therefore, using human SH-SY5Y neuroblastoma cells which can differentiate into dopaminergic neurons following treatment with retinoic acid, we first examined whether these cells express melatonin receptors. Subsequently, the physiological dose-dependent effects of melatonin on TH expression were examined in both undifferentiated and differentiated cells. The novel detection of the G protein-coupled melatonin MT(1) receptor in SH-SY5Y cells by RT-PCR was confirmed by sequencing and Western blotting. In addition, following treatment of SH-SY5Y cells with melatonin (0.1-100 nM) for 24h, Western analysis revealed a significant increase in TH protein levels. A biphasic response, with significant increases in TH protein at 0.5 and 1 nM melatonin and a reversal at higher doses was seen in undifferentiated cells; whereas in differentiated cells, melatonin was effective at doses of 1 and 100 nM. These findings suggest a physiological role for melatonin in modulating TH expression, possibly via the MT(1) receptor.

Kainic acid triggers oligodendrocyte precursor cell proliferation and neuronal differentiation from striatal neural stem cells

Glutamate is an excitatory amino acid that serves important functions in mammalian brain development through alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/ kainate receptor stimulation. Neural stem cells with self-renewal and multilineage potential are a useful tool to study the signals involved in the regulation of brain development. We have investigated the role played by AMPA/kainate receptors during the differentiation of neural stem cells derived from fetal rat striatum. The application of 1 and 10 microM kainic acid increased significantly the phosphorylation of the cyclic AMP response element binding protein (CREB), raised bromodeoxyuridine incorporation in O4-positive oligodendrocyte precursors, and increased the number of O1-positive cells in the cultures. Increased CREB phosphorylation and proliferation were prevented by the AMPA receptor antagonist 4-4(4-aminophenyl)-1,2-dihydro-1-methyl-2-propylcarbamoyl-6,7-methylenedioxyphthalazine (SYM 2206) and by protein kinase A and protein kinase C inhibitors. Cultures treated with 100 microM kainic acid showed decreased proliferation, a lower proportion of O1-positive cells, and apoptosis of O4-positive cells. None of these effects were prevented by SYM 2206, suggesting that kainate receptors take part in these events. We conclude that AMPA receptor stimulation by kainic acid promotes the proliferation of oligodendrocyte precursors derived from neural stem cells through a mechanism that requires the activation of CREB by protein kinase A and C. In the neurons derived from these cells, either AMPA or kainate receptor stimulation produces neuritic growth and larger cell bodies.

Carnosol, a component of rosemary (Rosmarinus officinalis L.) protects nigral dopaminergic neuronal cells

Carnosol, a major component of Rosmarinus officinalis, is a phenolic diterpene that has potent antioxidant and anti-inflammatory activities. In this study, we investigated the protective effects of carnosol on rotenone-induced neurotoxicity in cultured dopaminergic cells. Results showed that cell viability was significantly improved with carnosol through downregulation of caspase-3. Furthermore, carnosol significantly increased the tyrosine hydroxylase, Nurr1, and extracellular signal-regulated kinase 1/2. These results suggest that carnosol may have potential as a possible compound for the development of new agents to treat Parkinson's disease.

Intrastriatal Infusion of Liver Growth Factor Stimulates Dopamine Terminal Sprouting and Partially Restores Motor Function in 6-Hydroxydopamine-lesioned Rats

Liver growth factor (LGF) is a mitogen for liver cells that shows biological activity in extrahepatic sites and may be useful for neuroregenerative therapies. The aim of this work was to investigate the effects of the intrastriatal (IS) infusion of LGF in the 6-hydroxydopamine rat model of Parkinson's disease. Tyrosine hydroxylase-positive innervation was significantly increased in the dopamine-denervated striatum of rats receiving intrastriatal LGF infusions (160 ng/day/rat × 15 days) as compared with a vehicle-infused group. There was no evidence of dopaminergic neurogenesis in the striatum or substantia nigra in any experimental group at the times studied. However, in those animals undergoing IS-LGF infusion for 48 hr, we found a significant increase in both microglial proliferation and in the number of microglial cells that acquired the ameboid morphology. This is characteristic of activated microglia/macrophages that has been reported to play an important role in dopamine terminal sprouting. In summary, our study shows that IS infusion of LGF stimulates the outgrowth of tyrosine hydroxylase-positive terminals in the striatum of 6-hydroxydopamine-treated rats. As apomorphine-induced rotational behavior was also reduced in these animals, we propose LGF as a novel factor that, when delivered to the striatum, may be useful in the treatment of Parkinson's disease.

Mesenchymal stem cells spontaneously express neural proteins in culture and are neurogenic after transplantation

Reports of neural transdifferentiation of mesenchymal stem cells (MSCs) suggest the possibility that these cells may serve as a source for stem cell-based regenerative medicine to treat neurological disorders. However, some recent studies controvert previous reports of MSC neurogenecity. In the current study, we evaluate the neural differentiation potential of mouse bone marrow-derived MSCs. Surprisingly, we found that MSCs spontaneously express certain neuronal phenotype markers in culture, in the absence of specialized induction reagents. A previously published neural induction protocol that elevates cytoplasmic cyclic AMP does not upregulate neuron-specific protein expression significantly in MSCs but does significantly increase expression of the astrocyte-specific glial fibrillary acidic protein. Finally, when grafted into the lateral ventricles of neonatal mouse brain, MSCs migrate extensively and differentiate into olfactory bulb granule cells and periventricular astrocytes, without evidence of cell fusion. These results indicate that MSCs may be "primed" toward a neural fate by the constitutive expression of neuronal antigens and that they seem to respond with an appropriate neural pattern of differentiation when exposed to the environment of the developing brain.

Role of PKC-α,γ isoforms in regulation of c-Fos and TH expression after naloxone-induced morphine withdrawal in the hypothalamic PVN and medulla oblongata catecholaminergic cell groups

We previously demonstrated that morphine withdrawal induced hyperactivity of the hypothalamus-pituitary-adrenocortical axis by activation of noradrenergic pathways innervating the hypothalamic paraventricular nucleus (PVN), as evaluated by Fos expression and corticosterone release. The present study was designed to investigate the role of protein kinase C (PKC) in this process by estimating changes in PKCalpha and PKCgamma immunoreactivity, and whether pharmacological inhibition of PKC would attenuate morphine withdrawal-induced c-Fos expression and changes in tyrosine hydroxylase (TH) immunoreactivity levels in the PVN and nucleus tractus solitarius/ ventrolateral medulla (NTS/VLM). Dependence on morphine was induced in rats by 7 day s.c. implantation of morphine pellets. Morphine withdrawal was induced on day 8 by an injection of naloxone. The protein levels of PKCalpha and gamma were significantly down-regulated in the PVN and NTS/VLM from the morphine-withdrawn rats. Morphine withdrawal induced c-Fos expression in the PVN and NTS/VLM, indicating an activation of neurons in those nuclei. TH immunoreactivity was increased in the NTS/VLM after induction of morphine withdrawal, whereas there was a decrease in TH levels in the PVN. Infusion of calphostin C, a selective protein kinase C inhibitor, produced a reduction in the morphine withdrawal-induced c-Fos expression. Additionally, the changes in TH levels in the PVN and NTS/VLM were significantly modified by calphostin C. The present results suggest that activated PKC in the PVN and catecholaminergic brainstem cell groups may be critical for the activation of the hypothalamic-pituitary adrenocortical axis in response to morphine withdrawal.