Lithium chloride induces the expression of tyrosine hydroxylase in hNT neurons

Mesenchymal Stem Cell-Induced Anti-Neuroinflammation Against Traumatic Brain Injury

Traumatic brain injury (TBI) is a pervasive and damaging form of acquired brain injury (ABI). Acute, subacute, and chronic cell death processes, as a result of TBI, contribute to the disease progression and exacerbate outcomes. Extended neuroinflammation can worsen secondary degradation of brain function and structure. Mesenchymal stem cell transplantation has surfaced as a viable approach as a TBI therapeutic due to its immunomodulatory and regenerative features. This article examines the role of inflammation and cell death in ABI as well as the effectiveness of bone marrow-derived mesenchymal stem/stromal cell (BM-MSC) transplants as a treatment for TBI. Furthermore, we analyze new studies featuring transplanted BM-MSCs as a neurorestorative and anti-inflammatory therapy for TBI patients. Although clinical trials support BM-MSC transplants as a viable TBI treatment due to their promising regenerative characteristics, further investigation is imperative to uncover innovative brain repair pathways associated with cell-based therapy as stand-alone or as combination treatments.

Mesenchymal stem cell therapy alleviates the neuroinflammation associated with acquired brain injury

Ischemic stroke and traumatic brain injury (TBI) comprise two particularly prevalent and costly examples of acquired brain injury (ABI). Following stroke or TBI, primary cell death and secondary cell death closely model disease progression and worsen outcomes. Mounting evidence indicates that long‐term neuroinflammation extensively exacerbates the secondary deterioration of brain structure and function. Due to their immunomodulatory and regenerative properties, mesenchymal stem cell transplants have emerged as a promising approach to treating this facet of stroke and TBI pathology. In this review, we summarize the classification of cell death in ABI and discuss the prominent role of inflammation. We then consider the efficacy of bone marrow–derived mesenchymal stem/stromal cell (BM‐MSC) transplantation as a therapy for these injuries. Finally, we examine recent laboratory and clinical studies utilizing transplanted BM‐MSCs as antiinflammatory and neurorestorative treatments for stroke and TBI. Clinical trials of BM‐MSC transplants for stroke and TBI support their promising protective and regenerative properties. Future research is needed to allow for better comparison among trials and to elaborate on the emerging area of cell‐based combination treatments.

Complementation of dopaminergic signaling by Pitx3-GDNF synergy induces dopamine secretion by multipotent Ntera2 cells

Human teratocarcinoma cell line Ntera2 (NT2) expresses dopamine signals and has shown its safe profile for clinical applications. Attempts to restore complete dopaminergic (DAergic) phenotype enabling these cells to secrete dopamine have not been fully successful so far. We applied a blend of gene transfer techniques and a defined medium to convert NT2 cells to fully DAergic. The cells were primarily engineered to overexpress the Pitx3 gene product and then cultured in a growth medium supplemented with knockout serum and retinoic acid to form embroid bodies (EBs). Trypsinization of EB colonies produced single cells ready for differentiation. Neuronal/DAergic induction was promoted by applying conditioned medium taken from engineered human astrocytomas over-secreting glial cell-derived neurotrophic factor (GDNF). Immunocytochemistry, reverse-transcription and real-time polymerase chain reaction analyses confirmed significantly induced expression of molecules involved in dopamine signaling and metabolism including tyrosine hydroxylase, Nurr1, dopamine transporter, and aromatic acid decarboxylase. High-performance liquid chromatography analysis indicated release of dopamine only from a class of fully differentiated cells expressing Pitx3 and exposed to GDNF. In addition, Pitx3 and GDNF additively promoted in vitro neuroprotection against Parkinsonian toxin. One month after transplantation to the striatum of 6-OHDA-leasioned rats, differentiated NT2 cells survived and induced significant increase in striatal volume. Besides, cell implantation improved motor coordination in Parkinson's disease (PD) rat models. Our findings highlight the importance of Pitx3-GDNF interplay in dopamine signaling and indicate that our strategy might be useful for the restoration of DAergic fate of NT2 cells to make them clinically applicable toward cell replacement therapy of PD.

Lithium Improves Dopamine Neurotransmission and Increases Dopaminergic Protein Abundance in the Striatum after Traumatic Brain Injury

Experimental models of traumatic brain injury (TBI) recapitulate secondary injury sequela and cognitive dysfunction reported in patients afflicted with a TBI. Impairments in neurotransmission are reported in multiple brain regions in the weeks following experimental TBI and may contribute to behavioral dysfunction. Formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex is an important mechanism for neurotransmitter exocytosis. We previously showed that lithium treatment attenuated hippocampal decreases in α-synuclein and VAMP2, enhanced SNARE complex formation, and improved cognitive performance after TBI. However, the effect of TBI on striatal SNARE complex formation is not known. We hypothesized lithium treatment would attenuate TBI-induced impairments in evoked dopamine release and increase the abundance of synaptic proteins associated with dopamine neurotransmission. The current study evaluated the effect of lithium (1 mmol/kg/day) administration on striatal evoked dopamine neurotransmission, SNARE complex formation, and proposed actions of lithium, including inhibition of GSK3β, assessment of synaptic marker protein abundance, and synaptic proteins important for dopamine synthesis and transport following controlled cortical impact (CCI). Sprague-Dawley rats were subjected to CCI or sham injury and treated daily with lithium chloride or vehicle for 7 days post-injury. We provide novel evidence that CCI reduces SNARE protein and SNARE complex abundance in the striatum at 1 week post-injury. Lithium administration improved evoked dopamine release and increased the abundance of α-synuclein, D2 receptor, and phosphorylated tyrosine hydroxylase in striatal synaptosomes post-injury. These findings show that lithium treatment attenuated dopamine neurotransmission deficits and increased the abundance of synaptic proteins important for dopamine signaling after TBI.

Stem cell therapy for abrogating stroke-induced neuroinflammation and relevant secondary cell death mechanisms

Ischemic stroke is a leading cause of death worldwide. A key secondary cell death mechanism mediating neurological damage following the initial episode of ischemic stroke is the upregulation of endogenous neuroinflammatory processes to levels that destroy hypoxic tissue local to the area of insult, induce apoptosis, and initiate a feedback loop of inflammatory cascades that can expand the region of damage. Stem cell therapy has emerged as an experimental treatment for stroke, and accumulating evidence supports the therapeutic efficacy of stem cells to abrogate stroke-induced inflammation. In this review, we investigate clinically relevant stem cell types, such as hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs), very small embryonic-like stem cells (VSELs), neural stem cells (NSCs), extraembryonic stem cells, adipose tissue-derived stem cells, breast milk-derived stem cells, menstrual blood-derived stem cells, dental tissue-derived stem cells, induced pluripotent stem cells (iPSCs), teratocarcinoma-derived Ntera2/D1 neuron-like cells (NT2N), c-mycER(TAM) modified NSCs (CTX0E03), and notch-transfected mesenchymal stromal cells (SB623), comparing their potential efficacy to sequester stroke-induced neuroinflammation and their feasibility as translational clinical cell sources. To this end, we highlight that MSCs, with a proven track record of safety and efficacy as a transplantable cell for hematologic diseases, stand as an attractive cell type that confers superior anti-inflammatory effects in stroke both in vitro and in vivo. That stem cells can mount a robust anti-inflammatory action against stroke complements the regenerative processes of cell replacement and neurotrophic factor secretion conventionally ascribed to cell-based therapy in neurological disorders.

Lithium-induced neuroprotection in stroke involves increased miR-124 expression, reduced RE1-silencing transcription factor abundance and decreased protein deubiquitination by GSK3β inhibition-independent pathways

Lithium promotes acute poststroke neuronal survival, which includes mechanisms that are not limited to GSK3β inhibition. However, whether lithium induces long-term neuroprotection and enhanced brain remodeling is unclear. Therefore, mice were exposed to transient middle cerebral artery occlusion and lithium (1 mg/kg bolus followed by 2 mg/kg/day over up to 7 days) was intraperitoneally administered starting 0-9 h after reperfusion onset. Delivery of lithium no later than 6 h reduced infarct volume on day 2 and decreased brain edema, leukocyte infiltration, and microglial activation, as shown by histochemistry and flow cytometry. Lithium-induced neuroprotection persisted throughout the observation period of 56 days and was associated with enhanced neurological recovery. Poststroke angioneurogenesis and axonal plasticity were also enhanced by lithium. On the molecular level, lithium increased miR-124 expression, reduced RE1-silencing transcription factor abundance, and decreased protein deubiquitination in cultivated cortical neurons exposed to oxygen-glucose deprivation and in brains of mice exposed to cerebral ischemia. Notably, this effect was not mimicked by pharmacological GSK3β inhibition. This study for the first time provides efficacy data for lithium in the postacute ischemic phase, reporting a novel mechanism of action, i.e. increased miR-124 expression facilitating REST degradation by which lithium promotes postischemic neuroplasticity and angiogenesis.

Lithium's gene expression profile, relevance to neuroprotection A cDNA microarray study

Lithium can prevent 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) dopaminergic neurotoxicity in mice. This is attributed to induced antioxidant and antiapoptotic state, which among other factors results from induction of Bcl-2 and reduction of Bax, however, cDNA microarray reveals that this represents only one cascade of lithium targets. From analyzing the gene expression profile of lithium, we are able to point out candidate genes that might be involved in the antioxidant and neuroprotective properties of lithium. Among these are, the cAMP response element binding (CREB) protein, extracellular signal-regulated kinase (ERK), both CREB and ERK-part of the mitogen-activated kinase pathway-were upregulated by lithium, downregulated by MPTP, and maintained in mice fed with lithium chloride (LiCl) supplemented diet and treated with MPTP. Our positive control included tyrosine hydroxylase which both its mRNA and protein levels were independently measured, in addition to Bcl-2 protein levels. Other important genes which were similarly regulated are plasma glutathione peroxidase precursor (GSHPX-P), protein kinase C alpha type, insulin-like growth factor binding protein 4 precursor, and interferon regulatory factor. In addition, some genes were oppositely regulated, i.e., downregulated by lithium, upregulated by MPTP, and maintained in mice fed with LiCl supplemented diet and treated with MPTP, among these genes were basic fibroblast growth factor receptor 1 precursor, inhibin alpha subunit, glutamate receptor subunit zeta 1 precursor (NMD-R1), postsynaptic density protein-95 which together with NMD-R1 can form an apoptotic promoting complex. The discussed targets represent part of genes altered by chronic lithium. In fact lithium affected the expressions of more than 50 genes among these were basic transcription factors, transcription activators, cell signaling proteins, cell adhesion proteins, oncogenes and tumor suppressors, intracellular transducers, survival and death genes, and cyclins, here we discuss the relevance of these changes to lithium's reported neuroprotective properties.

Multiple transplants of hNT cells into the spinal cord of SOD1 mouse model of familial amyotrophic lateral sclerosis

hNT cells, derived from a human teratocarcinoma cell line, are versatile neuron-like cells that have been studied as possible treatment vehicles for neurodegenerative diseases. Previously, we showed the postponement of motor deficit symptoms in a G93A mouse model of amyotrophic lateral sclerosis (ALS) by transplanting hNT cells into the lumbar spinal cord. In this study, we examined the engraftment of hNT cells at multiple sites within the lumbar spinal cord by morphological analysis of neuritic process development. Results demonstrated that cells implanted at multiple sites established neuritic processes of different lengths independent of the number of cell implants. The hNT fiber outgrowth was a maximum of 0.15-0.3 mm from the transplants and mostly spread within the gray matter; interconnections between implants were not found. Therefore, we suggest that the observed postponement of motor deficit symptoms in G93A mice was not a result of neuritic outgrowth from the implanted hNT cells.

Cellular phenotypes of human model neurons (NT2) after differentiation in aggregate culture

The well-characterized human teratocarcinoma line Ntera2 (NT2) can be differentiated into mature neurons. We have significantly shortened the time-consuming process for generating postmitotic neurons to approximately 4 weeks by introducing a differentiation protocol for free-floating cell aggregates and a subsequent purification step. Here, we characterize the neurochemical phenotypes of the neurons derived from this cell aggregate method. During differentiation, the NT2 cells lose immunoreactivity for vimentin and nestin filaments, which are characteristic for the immature state of neuronal precursors. Instead, they acquire typical neuronal markers such as beta-tubulin type III, microtubule-associated protein 2, and phosphorylated tau, but no astrocyte markers such as glial fibrillary acidic protein. They grow neural processes that express punctate immunoreactivity for synapsin and synaptotagmin suggesting the formation of presynaptic structures. Despite their common clonal origin, neurons cultured for 2-4 weeks in vitro comprise a heterogeneous population expressing several neurotransmitter phenotypes. Approximately 40% of the neurons display glutamatergic markers. A minority of neurons is immunoreactive for serotonin, gamma-amino-butyric acid, and its synthesizing enzyme glutamic acid decarboxylase. We have found no evidence for a dopaminergic phenotype. Subgroups of NT2 neurons respond to the application of nitric oxide donors with the synthesis of cGMP. A major subset shows immunoreactivity to the cholinergic markers choline acetyl-transferase, vesicular acetylcholine transporter, and the non-phosphorylated form of neurofilament H, all indicative of motor neurons. The NT2 system may thus be well suited for research related to motor neuron diseases.

Norepinephrine and serotonin imbalance in the locus coeruleus in bipolar disorder

OBJECTIVES

Abnormalities in norepinephrine (NE) and serotonin (5-HT) are implicated in bipolar disorder (BD). We examined 5-HT input and NE neurons in the locus coeruleus (LC, the NE nucleus that innervates the forebrain) in BD by quantifying immunoreactivity (IR) for tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH), the biosynthetic enzymes for NE and 5-HT, respectively.

METHODS

Six suicides with BD were compared to matched normal controls and unipolar major depression suicides, using immunocytochemistry with computer-assisted quantification of immunoreactivity.

RESULTS

Depressed bipolar suicides had 26.7 +/- 1.3% of LC area occupied by the TH immunoreactive (TH-IR) process, while controls had 50.7 +/- 8% (p = 0.002) and unipolar depressed suicides had 50.3 +/- 2.5% (p = 0.003). In bipolars, these processes did not stain as darkly (1.9 +/- 0.5 x background) as controls (2.9 +/- 0.9 x background; p = 0.01) or unipolars (2.9 +/- 0.6 x background; p = 0.002). Bipolar suicides also had less TPH-IR processes in the LC (11.7 +/- 10%) compared with controls (32.8 +/- 8.8%; p = 0.01) or unipolar suicides (30.3 +/- 8%; p = 0.02). The TPH-IR intensity did not differ between groups.

CONCLUSIONS

We found less TH-IR and TPH-IR in the LC in depressed bipolar suicides, but not unipolar suicides, suggesting that both NE and 5-HT activity is lower in BD. Studies during manic or euthymic states will determine whether these changes are mood state dependent.

Transplantation of post-mitotic human neuroteratocarcinoma-overexpressing Nurr1 cells provides therapeutic benefits in experimental stroke: in vitro evidence of expedited neuronal differentiation and GDNF secretion

Nurr1 has been implicated as a transcription factor mediating the endogenous neuroprotective mechanism against stroke. We examined the in vivo and in vitro properties of a new human embryonic carcinoma Ntera-2 cell line carrying the human Nurr1 gene (NT2N.Nurr1). Adult Sprague-Dawley rats underwent experimental stroke initially and 14 days later were assigned randomly to receive stereotaxic transplantation of NT2N.Nurr1 cells or infusion of vehicle into their ischemic striatum. Transplantation of NT2N.Nurr1 cells promoted significant attenuation of behavioral impairments over a 56-day period after stroke, characterized by decreased hyperactivity, biased swing activity, and neurologic deficits, as well as significant reduction in ischemic striatal cell loss compared to vehicle-infused stroke animals. Transplanted NT2N.Nurr1 cells survived and expressed neuronal phenotypic markers in the ischemic striatum. In vitro results showed that cultured NT2.Nurr1 cells were already negative for nestin even before retinoic acid treatment, despite strong nestin immunoreactivity in NT2 cells. This indicates Nurr1 triggered a rapid commitment of NT2 cells into a neuronal lineage. Indeed, NT2.Nurr1 cells, at 4 weeks into RA treatment, displayed more abundant tyrosine hydroxylase positive cells than NT2 cells. Parallel ELISA studies showed further that cultured NT2N.Nurr1, but not NT2N cells, secreted glial cell derived neurotrophic factor. The present study shows efficacy of NT2N.Nurr1 cell grafts in ischemic stroke, with in vitro evidence suggesting the cells' excellent neuronal differentiation capability and ability to secrete GDNF as likely mechanisms mediating the observed therapeutic benefits.

Influence of retinoic acid and lithium on proliferation and dopaminergic potential of human NT2 cells

Our laboratory is working with the human NTera2/D1 (NT2) cell line, which has properties similar to those of progenitor cells in the central nervous system (CNS). These neural-like precursor cells can differentiate into all three major lineages, neurons, astrocytes, and oligodendrocytes. The pure neuronal population, hNT neurons, possess characteristics of dopamine (DA) cells. First, we analyzed whether the retinoic acid (RA)-treated hNT neurons and the NT2 precursor cells expressed two transcription factors required for development of the midbrain DA neurons. We report that NT2 cells endogenously expressed Engrailed-1 and Ptx3, whereas RA-treated hNT neurons did not express Engrailed-1 or Ptx3. Next we examined the influence of lithium treatment on Engrailed-1 and Ptx3 as well as another critical transcription factor, Nurr1. Previous research has shown that lithium can mimic the Wnt pathway, which is important for the induction of these transcription factors. Finally, we investigated the effect of lithium treatment on the viability and proliferation of NT2 cells, because lithium has been shown to stimulate neurogenesis in adult neural precursors. Lithium treatment increased the viability and proliferation of NT2 cells. The expression of transcription factors essential for the induction and maintenance of the DA phenotype was not increased in NT2 after lithium treatment. We conclude that the NT2 cell line is an excellent in vitro model system for studying the influence of pharmalogical agents on proliferation, differentiation, and apoptosis of a human neural progenitor cell line.

NTera2: a model system to study dopaminergic differentiation of human embryonic stem cells

NTera2, a human embryonal carcinoma (EC) stem cell line, shares many characteristics with human embryonic stem cells (hESCs). To determine whether NTera2 can serve as a useful surrogate for hESCs, we compared global gene expression between undifferentiated NTera2, multiple undifferentiated hESC cell lines, and their differentiated derivatives, and we showed that NTera2 cells share multiple markers with hESCs. Similar to hESCs, NTera2 cells differentiated into TH-positive cells that express dopaminergic markers including AADC, DAT, Nurr1, TrkB, TrkC, and GFRA1 when co-cultured with PA6 cells. Flow cytometry analysis showed that tyrosine hydroxylase (TH) and neural cell adhesion molecule (NCAM) expression increased, whereas SSEA4 expression decreased as cells differentiated. Medium conditioned by PA6 cells stimulated differentiation of NTera2 cells to generate TH-positive cells that expressed dopaminergic markers. Flow cytometry selected polysialylated (PSA-NCAM) cells responded to medium conditioned by PA6 cells by differentiating into TH-positive cells and expressed dopaminergic markers. Sorted cells differentiated for 4 weeks in PA6 cell conditioned media included functional neurons that responded to neurotransmitters and exhibited electronic excitability. Therefore, NTera2 cell dopaminergic neuronal differentiation and PSA-NCAM enrichment provides a useful system for the future study of hESCs.

Tumorigenicity issues of embryonic carcinoma-derived stem cells: relevance to surgical trials using NT2 and hNT neural cells

Cell therapy is a rapidly moving field with new cells, cell lines, and tissue-engineered constructs being developed globally. As these novel cells are further developed for transplantation studies, it is important to understand their safety profiles both prior to and posttransplantation in animals and humans. Embryonic carcinoma-derived cells are considered an important alternative to stem cells. The NTera2/D1 teratocarcinoma cell-line (or NT2-N cells) gives rise to neuron-like cells called hNT neurons after exposure to retinoic acid. NT2 cells form tumors upon transplantation into the rodent. However, when the NT2 cells are treated with retinoic acid to produce hNT cells, they terminally differentiate into post-mitotic neurons with no sign of tumorigenicity. Preliminary human transplantation studies in the brain of stroke patients also demonstrated a lack of tumorigenicity of these cells. This review focuses on the use of hNT neurons in cell transplantation for the treatment in central nervous system (CNS) diseases, disorders, or injuries and on the mechanism involved in retinoic acid exposure, final differentiation state, and subsequent tumorigenicity issues that must be considered prior to widespread clinical use.

Long distance selective fiber outgrowth of transplanted hNT neurons in white matter tracts of the adult rat brain

Terminally differentiated neurons derived from a human teratocarcinoma cell line (NT2N or hNT neurons) are promising as a cell source for transplantation, as they have been shown to be safe for transplantation in humans. We have shown previously that hNT neurons can express a catecholaminergic phenotype in a rat Parkinson model. In this study, we investigated the long-term survival and ability of hNT neurons to express tyrosine hydroxylase and reconstruct the dopamine-denervated nigrostriatal pathway. Hemiparkinsonian rats received grafts of 400,000 viable hNT neurons into each of the denervated striatum and substantia nigra. Robust hNT grafts were detected up to 24 weeks posttransplantation, although few cells expressed tyrosine hydroxylase. Many hNT fibers were often associated with ipsilateral and contralateral white matter tracts--corpus callosum, rostral migratory stream, optic tract, and external capsule. Fewer fibers were associated with the superior cerebellar peduncle, medial lemniscus, and nigrostriatal pathway. Axons also projected into the frontal cortex and extended parallel to the surface of the brain in the superficial cortical layers. These pathways were seen in all grafted animals, suggesting that specific guidance cues exist in the adult brain governing hNT fiber outgrowth. Injured adult axons and transplanted embryonic neuronal axons rarely extend for such distances in the adult nervous system. We propose that elucidating the factors promoting and guiding hNT axonal outgrowth could provide important clues to enhancing regeneration and target reinnervation in the adult brain, two factors of critical importance for cell restoration strategies aimed at brain repair.

Convergent effects of lithium and valproate on the expression of proteins associated with large dense core vesicles in NGF-differentiated PC12 cells

Lithium and valproate are chemically unrelated compounds that are used to treat manic-depressive illness. Previously, we reported that lithium ions upregulate genes encoding proteins primarily associated with large dense core vesicles (LDCV) in nerve growth factor (NGF)-differentiated PC12 cells, but not in undifferentiated PC12 cells. Moreover, lithium did not alter the expression of proteins associated with small-clear, synaptic-like vesicles (SSV) in these cells. Based on these observations, we investigated whether valproate had actions similar to those of lithium in PC12 cells. Thus, undifferentiated or NGF-differentiated PC12 cells were exposed to lithium (1 mM) or valproate (1 mM) for 48 h. Extracts from these cells were submitted to semiquantitative Northern and Western analyses. In NGF-differentiated cells, both agents increased the expression of proteins associated with LDCV, the vesicular monoamine transporter 1 (VMAT1), and cysteine string protein (CSP). These same treatments did not alter the expression of proteins primarily associated with SSV, the vesicular acetylcholine transporter (VAChT), and synaptophysin (SY). Furthermore, neither drug affected the expression of these proteins in undifferentiated cells. Interestingly, secretion of (3)H-dopamine was increased in cells exhibiting the increase of VMAT1 and csp. Taken together, the convergent effects of these chemically diverse compounds suggest that altered dynamics of LDCV may play a vital role in the biochemical pathway, leading to the relief of the symptoms of manic depression.

Studies on the differentiation of dopaminergic traits in human neural progenitor cells in vitro and in vivo

The development of cell replacement therapies for the treatment of neurodegenerative disorders such as Parkinson's disease (PD) may depend upon the successful differentiation of human neural stem/progenitor cells into dopamine (DA) neurons. We show here that primary human neural progenitors (HNPs) can be expanded and maintained in culture both as neurospheres (NSPs) and attached monolayers where they develop into neurons and glia. When transplanted into the 6-hydroxydopamine-lesioned rat striatum, undifferentiated NSPs survive longer (60% graft survival at 8-16 weeks vs. 30% graft survival at 8-13 weeks) and migrate farther than their attached counterparts. While both NSP and attached cells continue to express neuronal traits after transplantation, the spontaneous expression of differentiated transmitter-related traits is not observed in either cell type. However, following predifferentiation in culture using a previously described cocktail of reagents, approximately 25% of HNPs can permanently express the DA enzyme tyrosine hydroxylase (TH), even following replating and removal of the DA differentiation cocktail. When these predifferentiated HNPs are transplanted into the brain, however, TH staining is not observed, either because expression is lost or TH-expressing cells preferentially die. Consistent with the latter view is a decrease in total cell survival and migration, and an enhanced glial response in these grafts. In contrast, we found that the overall survival of HNPs is improved when cells engraft near blood vessels or CSF compartments or when they are placed into an intact unlesioned brain, suggesting that there are factors, as yet unidentified, that can better support the development of engrafted HNPs.

The transcription factor Nurr1 in human NT2 cells and hNT neurons

Human, neuronally committed hNT or NT2-N cells, originally derived from the Ntera2/D1 (NT2) clone after exposure to retinoic acid (RA), represent a potentially important source of cells to treat neurodegenerative diseases. Our previous in vitro experiments showed that hNT cells possess immunocytochemically detectable markers typical of dopaminergic (DA) ventral mesencephalic (VM) neurons, including tyrosine hydroxylase (TH), dopamine transporter (DAT), dopamine receptor (D2), and aldehyde dehydrogenase (AHD-2). In the current study, we sought to examine whether Nurr1, an orphan receptor of the nuclear receptor superfamily shown to be essential for the development, differentiation and survival of midbrain DA neurons, would be expressed in 3, 4, or 5 week RA-induced hNT neurons and their NT2 precursors. Our immunocytochemical analyses indicate that NT2 cells as well as hNT neurons independent of the length of RA-driven differentiation were Nurr1-immunoreactive. RT-PCR analysis confirmed the expression of Nurr1-specific mRNA in both NT2 precursors and the hNT neurons. Furthermore, immunocytochemical co-expression of Nurr1 and TH was detected in hNT neurons. The findings of this study suggest that Nurr1 may be important during the development of hNT neurons and involved in their differentiation into the dopaminergic phenotype.

Predicting response to lithium in mood disorders: role of genetic polymorphisms

Lithium is considered to be the first choice mood stabilizer in recurrent mood disorders. Its widespread and large-scale use is the result of its proven efficacy. In spite of this fact, patients have been observed to show a variable response to lithium treatment: in some cases it is completely effective in preventing manic or depressive relapses, while in other cases it appears to show no influence on the disease course. The possible definition of a genetic liability profile for adverse effects and efficacy will be of great help, as lithium therapy needs at least 6 months to be effective in stabilizing mood disorders. During the last few years, a number of groups have reported possible liability genes. Lithium long-term prophylactic efficacy has been associated with serotonin transporter protein, tryptophan hydroxylase and inositol polyphosphate 1-phosphatase variants. A number of other candidate genes and anonymous markers did not yield positive associations. Therefore, even if some positive results have been reported, no unequivocal susceptibility gene for lithium efficacy has been identified. Although the available data may not currently allow a meaningful prediction of lithium response, future research is aimed at the development of individualized treament of mood disorders, including the possibility of 'pharmacological genetic counseling'.

Lithium inhibitable enzymes in postmortem brain of bipolar patients

Despite considerable ongoing efforts at the epidemiological, genetic and molecular level, the etiology of bipolar disorder had not yet been elucidated. To study possible contributing components to the pathophysiology of this disorder, we have hypothesized that levels of enzymes inhibited by therapeutically relevant lithium ion concentrations in the brain of patients may differ from those in normal controls and may be involved in the etiology of the disorder. Three Li-inhibitable enzymes were studied in postmortem brain samples of bipolar patients and normal controls. The expression and function of the two enzymes that are obviously involved in signaling cascades, IMPase, involved in the second messenger system of the phosphatidylinositol cycle, and GSK-3, a mediator of an array of signaling cascades, were not found to be different in postmortem frontal and occipital cortex of bipolar patients and normal controls. Only PAP phosphatase protein levels, but not its mRNA levels or enzymatic activity, were found to be significantly decreased in frontal cortex of bipolar patients compared with normal controls.

Making and repairing the mammalian brain--in vitro production of dopaminergic neurons

Midbrain dopamine (DA) neurons play an essential role in modulating motor control, and their degeneration is the hallmark feature of Parkinson's disease (PD). In vitro production of DA neurons provides insight into the mechanisms that control cell fate choice, and offers an alternative to the use of fetal tissue for experimental cell replacement in PD. Here we will review the advantages and disadvantages of the various renewable cell sources and protocols tested, and discuss their relevance for basic studies and for cell therapy.

Lithium exposure enhances survival of NT2N cells (hNT neurons) in the hemiparkinsonian rat

Lithium (Li +) treatment of NTera2/D1 (or hNT Neurons) in culture increases tyrosine hydroxylase (TH) expression in this cell-line [Zigova et al., (1999) Exp. Neurol., 157, 251-258]. It is not known if these Li + treated cells maintain TH expression once transplanted into the striatum of the hemiparkinsonian rats. hNT neurons were either treated with 1 mm LiCl or left untreated and then transplanted into the striatum of Sprague-Dawley rats. Some cells were exposed to the lithium for 24 h in culture while others were exposed only briefly (2-3 h) just prior to transplantation. We also examined whether Li + treatment of the animal after transplantation (0.24% w/w lithium carbonate in chow) was effective in increasing neuronal survival. One week after transplantation, the animals were perfused with 4% paraformaldehyde and immunocytochemistry was performed on 30 micro m sections through the transplant. Human nuclear matrix antigen immunostaining demonstrated that there was significantly better survival of cells in the group treated briefly with lithium compared to all other groups. Brief exposure to lithium resulted in a greater expression of TH in situ as well. Neuron specific enolase immunohistochemistry showed that there was extensive fibre outgrowth in all groups. These results suggest that brief Li + exposure may enhance survival to over 60% and increase TH expression of hNT Neurons transplanted in the hemiparkinsonian rat nearly three-fold.

Nicotinic acetylcholine receptors on NT2 precursor cells and hNT (NT2-N) neurons

This is the first report, to our knowledge, of prominent, natural expression of nAChR alpha4, alpha6 and alpha9 subunits in a human, neuronally-committed cell line. We performed studies with specific reference to the expression of nicotinic acetylcholine receptors (nAChR) to further characterize a human, postmitotic, transplantable, with a neuronal phenotype, cell line called hNT (also called NT2-N). hNT cells acquire a distinctive neuronal phenotype upon differentiation from their NT2 precursors. Immunocytochemical studies showed that NT2 cells were strongly immunopositive for alpha4 or alpha7 subunits, moderately immunopositive for alpha3/alpha5 subunits, and weakly immunopositive for beta2 or beta4 subunits, whereas hNT neurons showed positive, strong-to-moderate immunostaining for all of these nAChR subunits. Reverse transcription-polymerase chain reaction (RT-PCR) mRNA analyses indicated that levels of alpha7 subunit messages were similar in both NT2 and hNT cells, whereas alpha2, alpha10, and beta3 subunit transcripts were not detected. Levels of alpha3, alpha5, and beta4 subunit messages were lower in hNT neurons than in NT2 precursors. However, alpha4 and beta2 subunit messages were present in NT2 precursors but were greatly induced in hNT neurons. Levels of alpha6 and alpha9 subunit messages, not detectable in NT2 precursors, rose to high levels in hNT neurons. hNT cell nAChR subunit message levels were comparable to (alpha4, alpha5, beta4) or higher than (alpha6, alpha9, beta2) levels in adult human brain. NT2 and hNT cells may provide an excellent model for studies of neurogenesis, roles played by nAChR in differentiation and neurodegeneration, and effects of neuronal differentiation on nAChR expression.

Lithium ions modulate the expression of VMAT2 in rat brain

Recent work has indicated that lithium (at 1 mM, a concentration that is efficacious in the treatment of manic-depressive disorders) modulates the level of vesicular monoamine transporter 1 (VMAT1) mRNA in PC12 cells as a function of the differentiation status of these cells. To ascertain whether VMAT expression in neurons is sensitive to lithium, in vivo, rats were fed a lithium-supplemented diet for 21 days (which raised serum lithium to 0.98+/-0.1 mM). Northern analysis revealed an overall increase (199+/-27%) of the neuronal VMAT isoform (VMAT2) in rat brain after lithium. However, in situ hybridization analysis revealed regional differences in the effects of lithium. Thus, VMAT2 mRNA increased by 50-100% over control in the raphe nuclei, ventral tegmental area, and substantia nigra of rats fed the lithium diet. Concomitantly, VMAT2 mRNA declined by about 50% in the locus coeruleus. Because VMAT2 is expressed in neurons that are strongly implicated in regulating mood and behavior, these data support the hypothesis that alterations of VMAT2 expression contribute to the therapeutic effects of lithium in psychiatric disorders.

3'(2')-phosphoadenosine 5'-phosphate phosphatase is reduced in postmortem frontal cortex of bipolar patients

OBJECTIVE

3'(2')-Phosphoadenosine 5'-phosphate (PAP) phosphatase is a novel lithium (Li) inhibitable enzyme. Thus the enzyme seemed an important candidate for studies of the molecular etiology of bipolar disorder.

METHODS

RT-PCR, Western-blot analysis and Pi liberation were used to measure PAP phosphatase mRNA levels, protein levels and enzyme activity (respectively) in postmortem frontal cortex specimens of bipolar patients versus normal subjects.

RESULTS

The PAP phosphatase protein levels were 24% significantly lower in bipolar patients than in normal subjects. PAP phosphatase mRNA levels and enzymatic activity did not differ between normal controls and bipolar patients.

CONCLUSIONS

Abnormality of PAP phosphatase in bipolar patients offers a new direction for study of bipolar disorder etiology.

Positive effect of transplantation of hNT neurons (NTera 2/D1 cell-line) in a model of familial amyotrophic lateral sclerosis

Transplantation of hNT Neurons derived from the human teratocarcinoma cell-line (NTera2/D1) has been shown to ameliorate motor dysfunction in a number of injury or disease models in which the deficits are fairly localized. However, these cells have not been used before in a model with more extensive neurodegeneration. The aim of this study is to determine the effects of hNT Neuron transplants on motor neuron function in a mouse model of familial amyotrophic lateral sclerosis (FALS) in which there is a substitution of Alanine for Glycine at position 93 of the human SOD1 gene (G93A). Amyotrophic lateral sclerosis is a fatal degenerative motor neuron disease affecting the spinal cord, brainstem, and cortex. This disease clinically manifests as progressive muscular weakness and atrophy, leading to paralysis and death within 3-5 years of diagnosis. The FALS represents 10-13% of all cases. A range of behavioral tests was used to examine spontaneous locomotor activity, coordination, and muscle strength of mice. Long-term (10-11 weeks) transplantation of hNT Neurons into the L(4)-L(5) segments of the ventral horn spinal cord of FALS(G93A) mice at 7 weeks of age (before onset of overt behavioral symptoms of disease) delayed the onset of motor dysfunction for at least 3 weeks. The average lifespan of the transplanted mice was 128 days compared to 106 days for media-injected group. The last mouse in the hNT Neuron transplanted group was euthanized at 135 days of age when it display partial paralysis of the hindlimbs. Immunohistochemical analysis of the implanted spinal cords demonstrated the survival of grafted hNT Neurons and showed many healthy-appearing motor neurons near the implant site. These results suggest that hNT Neuron transplantation may be a promising therapeutic strategy for ALS.

Pharmacogenetics in affective disorders

Pharmacogenetics will be of substantial help in the field of affective disorders pharmacotherapy. The possible definition of a genetic liability profile for drug side-effects and efficacy will be of great help in treatments that need weeks to months to be effective. During the last few years, a number of groups have reported possible liability genes. The efficacy and time of onset of selective serotonin reuptake inhibitors have been associated with a polymorphism in the promoter region of the transporter (SERTPR) in many independent studies, while variants at the tryptophan hydroxylase gene, 5-HT2a receptor and G-protein beta3 have been associated with them in pilot studies. Lithium long-term prophylactic efficacy has been associated with SERTPR, TPH and inositol polyphosphate 1-phosphatase variants, though in unreplicated samples. A number of further candidate genes were not associated with these treatments. In conclusion, both acute and long-term treatments appear to be, at least to some extent, under genetic influence and preliminary data have identified possible liability genes.

Lithium long-term treatment in mood disorders: clinical and genetic predictors

Lithium is the most widely used long-term treatment for recurrent mood disorders. Despite its proven efficacy, patients show a variable response, ranging from complete efficacy to no influence at all. This paper reviews possible predictors of response focusing on molecular genetic studies. The functional polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) has been associated with lithium long-term efficacy in two independent studies, marginal associations have been reported for tryptophan hydroxylase and inositol polyphosphate 1-phosphatase (INPP1). A number of other candidate genes and anonymous markers did not yield positive associations. Therefore, even though some positive results have been reported, no unequivocal susceptibility gene for lithium efficacy has been identified.

Differentiation of human dopamine neurons from an embryonic carcinomal stem cell line

Previous studies from this laboratory have demonstrated that fibroblast growth factor 1 together with a number of co-activator molecules (dopamine, TPA, IBMX/forskolin), will induce the expression of the catecholamine biosynthetic enzyme tyrosine hydroxylase (TH) in 10% of human neurons (hNTs) derived from the NT2 cell line [10]. In the present study, we found that TH induction was increased to nearly 75% in hNTs when cells were permitted to age 2 weeks in culture prior to treatment with the differentiation cocktail. This high level of TH expression was sustained 7 days after removal of the differentiating agents from the media. Moreover, the induced TH present in these cells was enzymatically active, resulting in the production of low levels of dopamine (DA) and its metabolite DOPAC. These findings suggest that hNTs may provide an important tissue culture model for the study of factors regulating TH gene expression in human neurons. Moreover, hNTs may serve, in vivo, as a source of human DA neurons for use in transplantation therapies.

The mood stabilizer valproic acid activates mitogen-activated protein kinases and promotes neurite growth

The mood-stabilizing agents lithium and valproic acid (VPA) increase DNA binding activity and transactivation activity of AP-1 transcription factors, as well as the expression of genes regulated by AP-1, in cultured cells and brain regions involved in mood regulation. In the present study, we found that VPA activated extracellular signal-regulated kinase (ERK), a kinase known to regulate AP-1 function and utilized by neurotrophins to mediate their diverse effects, including neuronal differentiation, neuronal survival, long term neuroplasticity, and potentially learning and memory. VPA-induced activation of ERK was blocked by the mitogen-activated protein kinase/ERK kinase inhibitor PD098059 and dominant-negative Ras and Raf mutants but not by dominant-negative stress-activated protein kinase/ERK kinase and mitogen-activated protein kinase kinase 6 mutants. VPA also increased the expression of genes regulated by the ERK pathway, including growth cone-associated protein 43 and Bcl-2, promoted neurite growth and cell survival, and enhanced norepinephrine uptake and release. These data demonstrate that VPA is an ERK pathway activator and produces neurotrophic effects.

Apoptosis in cultured hNT neurons

Programmed cell death (apoptosis) is an important mechanism shaping the size of different cell populations within the developing nervous system. In our study we used the NT2/D1 clone originally established from the Ntera 2 cell line to investigate the baseline levels of apoptosis in cultured postmitotic hNT (NT2-N) neurons previously treated for 3, 4 or 5 weeks with retinoic acid (RA) and compared it with apoptosis in NT2 precursors unexposed to RA. First, we examined whether different lengths of exposure to RA might affect baseline apoptotic rate in differentiating hNT neurons. Second, we investigated whether cultured hNT neurons, previously shown to possess dopaminergic characteristics, would be preferentially affected by apoptosis. Using the terminal deoxynucleotidyl transferase (tdt)-labeling technique we found that the postmitotic hNT neuronal cells exposed to RA demonstrated significantly higher numbers of apoptotic cells (12.5-15.8%) in comparison to rapidly dividing NT2 precursor cell line (3.6-4.4%) at both studied (1 and 5 days in vitro, DIV) time points. Similar apoptotic nuclear morphology, including a variable extent of nuclear fragmentation was observed in all examined hNT cultures. On the other hand, the incidence of apoptotic nuclei was rare in cultures of NT2 precursors not subjected to RA treatment. Combined immunocytochemistry for tyrosine hydroxylase (TH) and Hoechst staining revealed dopaminergic hNT neurons destined to die. Our double-labeling studies have demonstrated that only a subset of TH-positive hNT cells had condensed chromatin after 1 (approx. 15%) and 5 (approx. 20%) DIV. NT2 precursors were not TH-positive. Collectively, our results demonstrated that exposure to differentiating agent RA triggers an apoptotic commitment in a subset of postmitotic hNT neurons. These results suggest that this cell line may serve as a model of neuronal development to test various pathogenic factors implicated in the etiology of Parkinson's disease (PD), as well as to screen numerous pharmacological treatments that may slow or prevent dopaminergic deterioration.

Comparison of calcium-binding proteins expressed in cultured hNT neurons and hNT neurons transplanted into the rat striatum

An alternative source of cells for neural transplantation and brain repair that has many characteristics of immature neurons is the hNT neuron, derived from an embryonal human teratocarcinoma (NTera2) cell line that is terminally differentiated in vitro with retinoic acid. The majority of hNT neurons are GABAergic in cell culture. We have determined the calcium-binding protein (CBP) phenotypes of hNT neurons for three CBPs, calretinin (CR), calbindin D-28K (CB), and parvalbumin (PV), in cell culture and after transplantation into the rat striatum. In cell culture, 95% of all cell profiles were human nuclear matrix antigen (NuMA) positive. PV-positive hNT neurons constituted 50% of all neuron-like profiles, with CB+ and CR+ constituting 14 and 6% of cells, respectively. In contrast, when the striatal grafts were examined after 30 days survival using confocal microscopy, only 10% of hNT neurons immunopositive for NuMA were PV+; 19% were CB+/NuMA+, approximately the same percentage as was seen in vitro, and 82% of grafted hNT neurons were CR+. These results suggest that hNT neurons can be subdivided into at least three subpopulations based on the CBP phenotype that they express and that there is a CBP phenotypic shift following transplantation. Three related hypotheses are proposed to account for this phenotypic shift of hNT neurons after transplantation: (a) selective survival of the CR+ subpopulation of hNT neurons, (b) selective transitory quiescence of the transplanted PV+ cells due to transplantation stress, or (c) dedifferentiation of the hNT neurons following transplantation, which may allow them to respond to local environmental cues during the engraftment process.

The effects of taurine on hNT neurons transplanted in adult rat striatum

Taurine acts as an antioxidant able to protect neurons from free radical-mediated cellular damage. Moreover, it modulates the immune response of astrocytes that participate in neurodegenerative processes. The objective of this study was to examine whether taurine can prevent or attenuate the host inflammatory response induced by the xenotransplantation of neurons derived from the human teratocarcinoma cell line (hNT neurons). Male Sprague-Dawley rats were treated IP with either saline or taurine. Animals from both groups were perfused on the 4th or 11th day and the saline or taurine was administered from the start of the study until the day prior to sacrifice. The brains were processed immunohistochemically using antibodies against glial fibrillary acidic protein (GFAP), microglia (OX42), and human nuclear matrix antigen (NuMA). In the saline group, NuMA labeling revealed small grafts on the 4th day and no surviving cells on the 11th day. However, in the group that received taurine there were surviving grafts at both time points. Strong immunoreactivity for GFAP and OX42 was detected in the saline group surrounding the transplant. These effects were reduced in animals receiving taurine. Taken together, these results demonstrated that taurine was able to facilitate graft survival and attenuate the immune response generated by the xenograft.

In vitro and in vivo characterization of hNT neuron neurotransmitter phenotypes

The hNT neuron exhibits many characteristics of neuroepithelial precursor cells, making them an excellent model to study neuronal plasticity in vitro and in vivo. These cells express a number of neurotransmitters in vitro, including dopamine, gamma-aminobutyric acid and acetylcholine. However, there have been few reports of the neurotransmitters that hNT neurons express in vivo. The present study examined whether hNT neurons express the same neurotransmitters in vivo as they do in vitro. First, the expression of tyrosine hydroxylase (TH), glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT) and the human specific nuclear marker NuMA by hNT neurons was confirmed. Nineteen normal animals were then transplanted with 80,000 hNT neurons aimed at the striatum, hippocampus or cerebral cortex. Five additional animals received injections of medium. All animals received daily intraperitoneal injections of cyclosporine (10 mg/kg) and survived 30 days. Sections through the transplants were examined for NuMA-positive hNT neurons, and for the presence of the three neurotransmitter markers: TH, GAD and ChAT. The hNT neurons were found in the striatum and cortex. Of the hNT neurons found within the rat striatum, 33% were ChAT-positive. In the cortex, only 4% of the neurons expressed ChAT. No GAD-positive hNT neurons were detected at either site. No NuMA-positive neurons were found in the hippocampus. The implanted hNT neurons did not induce activation of astrocytes as determined by immunocytochemistry for glial fibrillary acidic protein (GFAP). Moreover, no hNT neuron was found to express GFAP in vivo. Together, these data suggest that the hNT neurons engraft in the new host tissue, maintain their neuronal identity and may be guided in differentiation according to local environmental cues.

Lithium regulates PKC-mediated intracellular cross-talk and gene expression in the CNS in vivo

It has become increasingly appreciated that the long-term treatment of complex neuropsychiatric disorders like bipolar disorder (BD) involves the strategic regulation of signaling pathways and gene expression in critical neuronal circuits. Accumulating evidence from our laboratories and others has identified the family of protein kinase C (PKC) isozymes as a shared target in the brain for the long-term action of both lithium and valproate (VPA) in the treatment of BD. In rats chronically treated with lithium at therapeutic levels, there is a reduction in the levels of frontal cortical and hippocampal membrane-associated PKC alpha and PKC epsilon. Using in vivO microdialysis, we have investigated the effects of chronic lithium on the intracellular cross-talk between PKC and the cyclic AMP (cAMP) generating system in vivo. We have found that activation of PKC produces an increase in dialysate cAMP levels in both prefrontal cortex and hippocampus, effects which are attenuated by chronic lithium administration. Lithium also regulates the activity of another major signaling pathway the c-Jun N-terminal kinase pathway--in a PKC-dependent manner. Both Li and VPA, at therapeutically relevant concentrations, increase the DNA binding of activator protein 1 (AP-1) family of transcription factors in cultured cells in vitro, and in rat brain ex vivo. Furthermore, both agents increase the expression of an AP-1 driven reporter gene, as well as the expression of several endogenous genes known to be regulated by AP-1. Together, these results suggest that the PKC signaling pathway and PKC-mediated gene expression may be important mediators of lithium's long-term therapeutic effects in a disorder as complex as BD.

Dopaminergic phenotype of hNT cells in vitro

We investigated the catecholaminergic nature of cultured hNT neurons previously treated either for 4 or 5 weeks with retinoic acid (RA). There were significantly more tyrosine hydroxylase (TH)-positive neurons (60%) in cultures treated for 4 weeks with RA compared to 5 week-treated cultures (</=15%). Furthermore, numerous TH-positive hNT cells were also immunoreactive to dopamine transporter (DAT), dopamine receptor (D2) and aldehyde dehydrogenase (AHD-2), an enzyme exclusively expressed by dopaminergic (DA) ventral mesencephalic (VM) precursors. Thus this cell line has all the necessary cellular machinery to produce functional DA neurons and therefore is a good alternative tissue source to fetal VM.

Human NT2 neurons express a large variety of neurotransmission phenotypes in vitro

The NT2 cell line, which was derived from a human teratocarcinoma, exhibits properties that are characteristic of a committed neuronal precursor at an early stage of development. NT2 cells can be induced by retinoic acid to differentiate in vitro into postmitotic central nervous system (CNS) neurons (NT2-N cells). The commitment of NT2-N cells to a stable neuronal phenotype is irreversible. Because it may be possible to transplant these human neurons to compensate for neuronal loss after traumatic injuries or neurodegenerative diseases of the CNS, knowledge of their phenotype is essential. This study aimed to characterize in detail the neurotransmission phenotype of NT2-N cells by using immunocytochemical methods. Single peroxidase immunostaining demonstrated that NT2-N cells expressed the gamma-aminobutyric acidergic (GABAergic), catecholaminergic, and cholinergic phenotypes to a large extent and expressed the serotonergic phenotype to a minor extent. NT2-N cells also expressed different neuropeptides, such as neuropeptide Y, oxytocin, vasopressin, calcitonin gene-related peptide, and Met- and Leu-enkephalin. Double fluorescence immunostaining further indicated that a large number of NT2-N cells could express GABA and another neurotransmitter or neuropeptide at the same time. Finally, electron microscopy demonstrated that these NT2 neurons elaborate classical synaptic contacts. The multipotentiality of these neurons, combined with their apparent functionality, suggests that they may represent useful material for a variety of therapeutic approaches aimed at replacing dead neurons after neurodegenerative diseases or lesions of the CNS.

The properties of hNT cells following transplantation into the subventricular zone of the neonatal forebrain

Neurons derived from the human teratocarcinoma cell line (hNT) establish structural polarity and a fully mature phenotype following transplantation into the rodent brain. Here we describe the transplantation of hNT cells into the anterior part of neonatal subventricular zone (SVZa), which is a prolific region of neuronal progenitor cells. Ordinarily, the progeny of endogenous or homotopically transplanted SVZa cells migrate to the olfactory bulb (OB) along a restricted pathway, the rostral migratory stream (RMS), and differentiate into interneurons. To compare the phenotype of cultured hNT cells to their transplanted cohorts, hNT cells labeled by the fluorescent dye PKH26 were cultured for 1 day and stained with cell-type-specific antibodies. Clusters as well as individual hNT cells were immunoreactive for TuJ1, an antibody that recognizes neuron-specific class III beta-tubulin. The distribution and phenotype of the transplanted hNT cells were examined. The majority of transplanted PKH26-labeled hNT cells were found at their site of implantation in the SVZa, while a small proportion of the transplanted hNT cells was situated in the migratory pathway leading to the OB and in the subependymal zone and granule cell layer of the olfactory bulb. Many of the transplanted hNT cells, both within the SVZa and within the RMS, revealed a neuronal phenotype. Collectively, these results reveal the capacity of hNT cells to respond, at least partially, to cues that ordinarily govern the migration of SVZa-derived cells and maintain their neuronal identity.

Intrastriatal and intranigral grafting of hNT neurons in the 6-OHDA rat model of Parkinson's disease

The clinical findings on neural transplantation for Parkinson's disease (PD) reported thus far are promising but many issues must be addressed before neural transplantation can be considered a routine therapeutic option for PD. The future of neural transplantation for the treatment of neurological disorders may rest in the discovery of a suitable alternative cell type for fetal tissue. One such alternative may be neurons derived from a human teratocarcinoma (hNT). hNT neurons have been shown to survive and integrate within the host brain following transplantation and provide functional recovery in animal models of stroke and Huntington's disease. In this study, we describe the transplantation of hNT neurons in the substantia nigra (SN) and striatum of the rat model for PD. Twenty-seven rats were grafted with one of three hNT neuronal products; hNT neurons, hNT-DA neurons, or lithium chloride (LiCl) pretreated hNT-DA neurons. Robust hNT grafts could be seen with anti-neural cell adhesion molecule and anti-neuron-specific enolase immunostaining. Immunostaining for tyrosine hydroxylase (TH) expression revealed no TH-immunoreactive (THir) neurons in any animals with hNT neuronal grafts. THir cells were observed in 43% of animals with hNT-DA neuronal grafts and all animals with LiCl pretreated hNT-DA neuronal grafts (100%). The number of THir neurons in these animals was low and not sufficient to produce significant functional recovery. In summary, this study has demonstrated that hNT neurons survive transplantation and express TH in the striatum and SN. Although hNT neurons are promising as an alternative to fetal tissue and may have potential clinical applications in the future, further improvements in enhancing TH expression are needed.

Lithium activates the c-Jun NH2-terminal kinases in vitro and in the CNS in vivo

The therapeutic efficacy of lithium in the treatment of mood disorders is delayed and only observed after chronic administration, a temporal profile that suggests alterations at the genomic level. Lithium has been demonstrated to modulate AP-1 DNA binding activity as well as the expression of genes regulated by AP-1, but the mechanisms underlying these effects have not been fully elucidated. In the present study, we found that the lithium-induced increases in AP-1 DNA binding activity were accompanied by increases in p-cJun and cJun levels in SH-SY5Y cells. Lithium also increased cJun-mediated reporter gene expression in a dose-dependent manner, with significant effects observed at therapeutically relevant concentrations. Lithium's effects on cJun-mediated reporter gene expression in SH-SY5Y cells were more pronounced in the absence of myo-inositol and were blocked by protein kinase C (PKC) inhibitors and by cotransfection with a PKCalpha dominant-negative mutant. Chronic in vivo lithium administration increased AP-1 DNA binding activity in frontal cortex and hippocampus and also increased the levels of the phosphorylated, active forms of c-Jun NH2-terminal kinases (JNKs) in both brain regions. These results demonstrate that lithium activates the JNK signaling pathway in rat brain during chronic in vivo administration and in human cells of neuronal origin in vitro; in view of the role of JNKs in regulating various aspects of neuronal function and their well-documented role in regulating gene expression, these effects may play a major role in lithium's long-term therapeutic effects.