![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
CELLULAR AND MOLECULAR
Neuroimmunology Laboratory, Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Medical School, Minneapolis, Minnesota (S.H., M.C.-J.C., W.S.S., J.R.L., P.K.P.); and Stem Cell Department, R&D Systems, Inc., Minneapolis, Minnesota (H.T.N.)
Received February 28, 2006; accepted June 8, 2006.
 |
Abstract |
|---|
 Top Abstract Materials and MethodsResultsDiscussionReferences |
|---|
), a finding that correlated with cocaine-induced down-regulation of CXCR4 on NPCs. Finally, these data demonstrated that NPCs exposed to cocaine underwent differentiation into cells expressing neuronal markers that was associated with an inhibition of SOX2 (SRY-related HMG-box gene 2), a transcription factor that inhibits NPC differentiation. Taken together, these results point to several cellular mechanisms whereby exposure of human neural stem cells to cocaine in utero could contribute to subsequent neurodevelopmental and neurocognitive deficits.
; Singer et al., 2002). It seems that cocaine-induced cognitive abnormalities that are detectable during the first 2 years of life continue to contribute to learning difficulties at school age (Singer et al., 2002). Although the mechanisms responsible for the effect of cocaine on the developing human brain are unknown, administration of cocaine to pregnant animals is associated with permanent morphological abnormalities of the brain and sustained cognitive deficits in the offspring (Lidow and Song, 2001; Harvey, 2004).
During the past several years, increased attention has been focused on the biological role of neural stem cells (NSCs) in brain development (McKay, 1997; Piper et al., 2000; Uchida et al., 2000; Sommer and Rao, 2002) as well as during neurogenesis in the adult brain (Gage et al., 1998; Kempermann, 2002; Nunes et al., 2003). Based on their functional properties of self-renewal (i.e., sustained proliferative capacity), motility (i.e., migration throughout the brain), and multipotency (i.e., ability to differentiate into glial cells or neurons), NSCs have been considered as a potential therapeutic modality for brain repair (Cao et al., 2002; Peterson, 2002; Hallbergson et al., 2003). In addition, NSC cultures have been increasingly used as models of neurodegenerative disorders (Jakel et al., 2004) and as pharmacological tools for evaluating the neurotoxic and therapeutic potential of drugs (Conti et al., 2003). Thus far, however, relatively few psychoactive agents have been evaluated in these models, and little or nothing is known about the effects of cocaine on NSCs. In the present study, a cell culture model of highly enriched human fetal brain-derived neural precursor cells (NPCs) (Ni et al., 2004), which share the functional properties of NSCs, was used to assess the effects of cocaine on these neural progenitors.
|
Materials and Methods |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
, anti-human nestin, anti-human Tuj1, anti-human CXCR4, and anti-human SOX2 antibodies (R&D Systems, Minneapolis, MN); fetal bovine serum (Hyclone, Logan, UT); [3H]thymidine (GE Healthcare, Piscataway, NJ); 5-bromo-2'-deoxyuridine (BrdU) and anti-BrdU antibody (Roche, Indianapolis, IN); anti-human glial fibrillary acidic protein (GFAP) antibody (Sternberger Monoclonals, Lutherville, MD); anti-PCNA antibody (BD Biosciences, San Diego, CA); 4,6-diamidino-2-phenylindole (Intergen, Purchase, NY); and gp120 (Protein Sciences, Meriden, CT).
NPC Cultures. NPC cultures were prepared from 7- to 9-weekold human fetal brain as described previously (Ni et al., 2004). Human fetal brain tissues obtained under a protocol approved by our Human Subjects Research Committee were mechanically dissociated, resuspended in Dulbecco's modified Eagle's medium/F-12 medium (containing 8 mM glucose and glutamine; N2 plus supplement; penicillin and streptomycin; and 20 ng/ml human hFGFb/20 ng/ml hEGF) and plated onto poly-D-lysine-coated 10-cm tissue culture dishes or 24-well plates when indicated. This stage is considered as passage 0. When cell cultures reached 50 to 60% confluence, they were subcultured using trypsin removal (0.0125%) at a density of 2 x 105 cells per 10-cm culture dish and considered as passage 1. Medium was replaced every other day. NPC cultures at passages 1 to 3 were used throughout the study. These NPCs express the neural stem cell markers nestin (>90% positive) and CD133 (>80% positive) and are GFAP (a marker for astrocytes)-negative and microtubule-associated protein 2 (a neuronal cell marker)-negative (Ni. et al., 2004).
NPC Proliferation Assay. Cocaine (10-10 to 10-4 M) was added one day after plating NPCs onto 24-well culture plates or 4-well chamber slides (1 x 102 cells per well) and was re-added every other day during culture medium replacement for a total of 7 days. Either [3H]thymidine was added to the 24-well plates (1 µCi per well) and incubated overnight before being harvested and measured for [3H]thymidine incorporation in a 
-counter or BrdU (10 µg/ml) was added to NPC chamber slides overnight before being fixed and stained with anti-BrdU antibody.
NPC Differentiation Assay. Two experimental paradigms were used. 1) One day after plating NPCs onto four-chamber slides (1 x 102 cells per well), NPC cultures were treated with cocaine (10-8, 10-6, and 10-4 M) for 7 days with medium and cocaine replacement every other day. NPC culture slides were fixed with 4% paraformaldehyde and stained for nestin, Tuj1 (a neuronal marker), and GFAP. 2) Seven days after plating NPCs onto 10-cm culture dishes (2 x 105 cells per dish) with medium replacement every other day, NPC (50-60% confluence) were subjected to cocaine treatment (10-8, 10-6, and 10-4 M) for 7 days following withdrawal of growth factors. At the designated time point, NPCs were collected for flow-cytometric analysis for differentiation into neuronal and astrocytic cell populations.
NPC Migration Assay. NPCs were added to upper chambers of a 96-well chemotaxis device (Neuro Probe Inc., Gaithersburg, MD) (106 cells/well) separated from the lower chambers with an 8-µm pore size of polyvinylpyrrolidone-free polycarbonate filter. The lower chambers were filled with chemoattractants. After 6 h of incubation, NPCs that had migrated from upper chambers into lower chambers were quantified by Diff-Quik staining (Dade Diagnostics, Aguada, PR). To determine the effect of blockade of CXCR4, NPCs were treated with anti-CXCR4 antibody (10 µg/ml) or human immunodeficiency virus type 1 (HIV-1) gp120 (10-9 and 10-8 M) for 30 min before being used in chemotaxis assay toward CXCL12/SDF-1.
Immunocytochemical Staining. Anti-nestin, anti-Tuj1, and anti-BrdU antibodies were used at the concentration of 10 µg/ml on fixed cells. Anti-GFAP antibody was used at 1:200 dilution. Cells were fixed with 4% paraformaldehyde and 0.15% picric acid in PBS at room temperature for 20 min and were then permeated and blocked with 0.1% Triton X-100, 1% bovine serum albumin, and 10% normal donkey serum in PBS at room temperature for 45 min. After blocking, cells were incubated with diluted primary antibody overnight at 4°C and sequentially with fluorescence-coupled anti-mouse IgG Ab (Jackson Laboratory, Bar Harbor, ME) at room temperature in the dark for 1 h. Cells were washed between each step with 0.1% bovine serum albumin in PBS.
Flow Cytometry. Staining of cells with mouse anti-human SOX2-phycoerythrin and anti-human CXCR4 receptor-phycoerythrin antibodies was performed according to the manufacturer's suggested procedures. For nestin staining, cells were fixed with 4% paraformaldehyde in PBS at room temperature for 20 min and washed twice with PBS. After washing, cells were resuspended in saponin-containing buffer (2% fetal calf serum, 0.5% saponin, and 0.1% sodium azide in PBS), and mouse anti-human nestin or mouse IgG1 isotype control antibody (R&D Systems) was added at the final concentration of 10 µg/ml to 2.5 x 105 cells in a total reaction volume of 200 µl. After incubation for 20 min at room temperature, excess nestin or isotype control antibody was removed by washing with SAP buffer, and cells were resuspended in 200 µl of SAP buffer with 1 µg of goat anti-mouse IgG-fluorescein isothiocyanate (Caltag, San Francisco, CA). The samples were incubated for 20 min in the dark at room temperature, washed once each with SAP buffer and PBS, resuspended in 400 µl of PBS, and analyzed on a FACScan flow cytometer. Five thousand events were collected and analyzed using CellQuest software (Becton-Dickinson, Mountain View, CA).
Cell Death Detection ELISA. To measure apoptosis, cell lysates from culture medium- or cocaine-treated NPC cultures in 24-well plates were collected for histone-associated DNA fragmentation measurement according to the manufacturer's protocol. In brief, cell lysates were added to the streptavidin-coated 96-well ELISA plates together with anti-histone-biotinylated and anti-DNA-peroxidase antibodies. After incubation and washing, DNA fragments were captured and detected by a chromogenic enzyme-substrate reaction.
Statistical Analysis. Data are expressed as mean ± S.E.M. For comparison of means of multiple groups, ANOVA was used, followed by Scheffe's test.
|
Results |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
10-6 M, as assessed by [3H[thymidine uptake (Fig. 1A). Because the pharmacological action of the naturally occurring enantiomer (-)-cocaine is thought to involve inhibition of biogenic amine transporters, a process that is not observed with (+)-cocaine, we compared the effects of the two enantiomers on NPC proliferation. As is shown in Fig. 1B, the unnatural enantiomer had no effect on the proliferative activity of NPCs. Next, the [3H]thymidine uptake assay was used to evaluate a time course of cocaine-induced inhibition of NPC proliferation. Within 3 days of exposure to cocaine (10-6 M), NPC proliferative activity was found to be markedly impaired, and this inhibitory effect was even more pronounced at the end of the 7-day assay period (Fig. 1C). When examined using immunochemistry, a marked decrease in the number of proliferative cells was observed following cocaine treatment (10-6 M), as judged by their ability to incorporate BrdU (Fig. 1D).
|
To determine whether the inhibition of NPC proliferation by cocaine was related to induction of cell death, apoptosis of the treated NPCs was quantified after 7 days of culture in the absence (control) or presence of cocaine at doses ranging from 10-12 to 10-4 M. Because human NPCs are known to express the chemokine coreceptor CXCR4 (Ni et al., 2004), which is a binding site for HIV-1 gp120, we included gp120 in this experiment as a positive control. These experiments showed that, in marked contrast to gp120 (10 nM), which induced significant apoptosis, cocaine treatment itself did not affect NPC survival, as assessed using an ELISA for histone-associated DNA fragments (Fig. 2A). Even though cocaine by itself had no effect on cell survival, when it was added along with varying concentrations of gp120, it potentiated gp120-induced NPC apoptosis (Fig. 2B).
|
|
Effect of Cocaine on NPC Migratory Activity. Another defining feature of NSCs is their ability to migrate to areas distal to the ventricular and subventricular zones where they originate. Although the processes that govern NSC migration within the nervous system are incompletely understood, CXCL12 recently has been shown to regulate migration of sensory neural progenitors in the mouse embryo (Belmadani et al., 2005), and human NPCs are known to migrate toward this CXCR4 ligand in vitro (Ni et al., 2004). Thus, we next studied the effect of treatment of NPCs with cocaine on their migratory response to CXCL12. As is shown in Fig. 4A, cocaine inhibited the migratory activity of NPCs in a concentration-dependent manner. Because this migratory response involves CXCR4, which is expressed on a large majority of NPCs (Ni et al., 2004), we used flow cytometry to test the hypothesis that cocaine treatment would be associated with down-regulation of CXCR4 expression, as a potential explanation of this inhibitory effect of cocaine. In support of this hypothesis, cocaine (10-6 M) down-regulated the expression of CXCR4 on treated NPCs (Fig. 4B). Although 96% of untreated (control) NPCs expressed CXCR4, only 68% of cocaine-treated cells expressed this chemokine receptor. In addition, the intensity of fluorescence was diminished by cocaine treatment, indicating that, in addition to fewer cells displaying CXCR4, the total number of receptors was reduced after exposure to cocaine.
|
Effect of Cocaine on NPC Differentiation. Human NPCs that are maintained in culture medium containing the growth factors hFGFb and hEGF do not express markers indicative of differentiation into neurons or glia (Ni et al., 2004). To determine whether exposure of NPCs to cocaine affects the expression of cellular differentiation markers, cocaine was added to the growth factor-containing medium, and the cells were examined by immunocytochemistry for the presence of Tuj1 and GFAP. After 7 days of culture in medium containing cocaine (10-6 M), the morphology of NPCs differed from that of untreated cells, and the cocaine-treated NPC cultures harbored a considerable number of cells that expressed Tuj1 (Fig. 5A) but few of which expressed GFAP (Fig. 5B). These data demonstrate that cocaine treatment induced cellular differentiation of the NPCs into cells possessing a neuronal but not an astrocytic phenotype.
|
), we hypothesized that exposure of these cells to cocaine would result in down-regulation of the constitutive expression of SOX2 as a potential mechanism, whereby cocaine induces the differentiation of NPCs into neurons. To test this hypothesis, NPCs were both left untreated or treated with cocaine, and SOX2 expression was assessed using fluorescence-activated cell sorting analysis. Whereas untreated (control) NPCs expressed SOX2 (Fig. 6A), treatment with cocaine (10-6 M) for 3 days completely suppressed SOX2 expression (Fig. 6B). These results demonstrate that cocaine treatment of NPCs is able to down-regulate the expression of transcription factors that are required for stem cell maintenance.
|
|
Discussion |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
; Sommer and Rao, 2002), and cell culture models, such as the one used in this study, can provide potentially valuable insight regarding the mechanisms, whereby extrinsic factors affect the fate of neuroprogenitors. The results of the present study of human fetal brain-derived NPC cultures indicate that cocaine is another extrinsic factor that can significantly affect three critical functional properties of NSCs. First, cocaine treatment was shown to inhibit the proliferation of NPCs, a phenomenon that was associated with cell-cycle arrest, which appeared to be due to increased expression of the cyclin-dependent kinase inhibitor p21. Second, treatment of NPCs with cocaine inhibited their migratory response to CXCL12, a finding that was associated with cocaine-induced down-regulation of CXCR4 on NPCs. Third, NPCs exposed to cocaine underwent changes indicative of differentiation into neurons, which was associated with an inhibition of SOX2, a transcriptional factor that inhibits NSC differentiation. Although additional work is required for a comprehensive understanding of how cocaine alters each of these cellular processes, as well as to determine whether the effects we observed were mediated by cocaine itself or by a metabolite generated by NPCs, these findings provide initial information regarding several mechanisms that could underlie the effects of cocaine on neurogenesis in the human brain.
Previous in vitro studies investigating the effects of cocaine on neuroglioblastoma cells (Johnson and Weissman, 1988), PC-12 cells (Zachor et al., 1994), and cortical neurons of fetal mice (Nassogne et al., 1997), as well as in utero exposure to cocaine administered to pregnant animals (Mayes, 1999; Lidow and Song, 2001; Harvey, 2004), support the notion that cocaine has a variety of adverse effects on neurodevelopment. Because of potential differences among animal species, the use of human neuroprogenitors to model neurological disease has been recommended (Jakel et al., 2004). Thus, although the biological significance of the findings in the present study must be interpreted with caution, because they were derived using an in vitro NPC culture model, they point to cellular mechanisms, whereby exposure of human NSCs to cocaine in utero could contribute to subsequent neurocognitive deficits.
Of the different classes of psychoactive drugs that have potential for abuse, to date opiates have been the best studied in terms of their effects on NSCs. These studies, which have used various in vitro and experimental rodent models, have shown that exposure of embryonic and adult neuroprogenitor cells to opiates inhibits neurogenesis (Eisch et al., 2000; Hauser et al., 2000; Persson et al., 2003; Mandyam et al., 2004). In one study of mixed glial cell cultures isolated from 1-day-old mouse striatum, morphine was found to synergistically increase HIV-1 Tat protein-mediated cytotoxicity of glial cell precursors (Khurdayan et al., 2004). This observation is interesting in light of the finding in the present study that, while cocaine by itself had no effect on cell survival, it synergistically increased HIV-1 gp120-induced apoptosis of human NPCs. This synergistic activity of cocaine is consistent with the report that subchronic administration of cocaine in rats had no effect on viability of cortical neurons but that cocaine significantly enhanced neuronal apoptosis induced by gp120 (Bagetta et al., 2004). In addition, the finding in the present study that gp120 induces apoptosis of human NPCs adds to recent evidence that interactions of gp120 with NSCs may contribute to HIV-1 neuropathogenesis (Krathwohl and Kaiser, 2004; Tran et al., 2005).
Because neurogenesis in the adult brain is associated with memory formation and learning (Gould et al., 1999; Shors et al., 2001), the findings in the present study using human NPCs may also have relevance to the development of neurocognitive deficits of adults who are using cocaine. Mounting evidence from studies of other substances of abuse, including alcohol, suggests that alterations in neurogenesis may be involved in their neurobehavioral effects (Duman et al., 2001; Powrozek et al., 2004; He et al., 2005), and it also appears that NSC proliferation may underlie the therapeutic effect of certain antipsychotic agents (Kippin et al., 2005). Although in vitro studies have major limitations and great caution is needed in extrapolating these findings to the clinical arena, it is possible that the human NPC cultures used in the present study could be applicable not only as a model to study cocaine-induced neurotoxicity but also to investigate the potential involvement of NSCs in the process of cocaine dependence.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
ABBREVIATIONS: NSC, neural stem cell; NPC, neural precursor cells; hFGFb, human fibroblast growth factor-basic; hEGF; human epidermal growth factor; CXCR, CXC chemokine receptor; CXCL, CXC chemokine ligand; SDF-1, stromal cell-derived factor-1; PCNA, proliferating cell nuclear antigen; BrdU, 5-bromo-2'-deoxyuridine; GFAP, glial fibrillary acidic protein; PBS, phosphate-buffered saline; HIV-1, human immunodeficiency virus type 1; ELISA, enzyme-linked immunosorbent assay; SOX2, SRY-related HMG-box gene 2.
Address correspondence to: Dr. Phillip K. Peterson, Center for Infectious Diseases and Microbiology Translational Research, 3-216 LRB/MTRF, 2001 6th Street S.E., University of Minnesota Medical School, Minneapolis, MN 55455. E-mail: peter137{at}umn.edu
|
References |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
Bagetta G, Piccirilli S, Del Duca C, Morrone LA, Rombola L, Nappi G, De Alba J, Knowles RG, and Corasaniti MT (2004) Inducible nitric oxide synthase is involved in the mechanisms of cocaine enhanced neuronal apoptosis induced by HIV-1 gp120 in the neocortex of rat. Neurosci Lett 356: 183-186.[CrossRef][Medline]
Belmadani A, Tran PB, Ren D, Assimacopoulos S, Grove EA, and Miller RJ (2005) The chemokine stromal cell-derived factor-1 regulates the migration of sensory neuron progenitors. J Neurosci 25: 3995-4003.
Cameron HA, Hazel TG, and McKay RD (1998) Regulation of neurogenesis by growth factors and neurotransmitters. J Neurobiol 36: 287-306.[CrossRef][Medline]
Cao Q, Benton RL, and Whittemore SR (2002) Stem cell repair of central nervous system injury. J Neurosci Res 68: 501-510.[CrossRef][Medline]
Conti L, Cataudella T, and Cattaneo E (2003) Neural stem cells: a pharmacological tool for brain diseases? Pharmacol Res 47: 289-297.[CrossRef][Medline]
Duman RS, Malberg J, and Nakagawa S (2001) Regulation of adult neurogenesis by psychotropic drugs and stress. J Pharmacol Exp Ther 299: 401-407.
Eisch AJ, Barrot M, Schad CA, Self DW, and Nestler EJ (2000) Opiates inhibit neurogenesis in the adult rat hippocampus. Proc Natl Acad Sci USA 97: 7579-7584.
Gage FH, Kempermann G, Palmer TD, Peterson DA, and Ray J (1998) Multipotent progenitor cells in the adult dentate gyrus. J Neurobiol 36: 249-266.[CrossRef][Medline]
Gould E, Beylin A, Tanapat P, Reeves A, and Shors TJ (1999) Learning enhances adult neurogenesis in the hippocampal formation. Nat Neurosci 2: 260-265.[CrossRef][Medline]
Graham V, Khudyakov J, Ellis P, and Pevny L (2003) SOX2 functions to maintain neural progenitor identity. Neuron 39: 749-765.[CrossRef][Medline]
Hallbergson AF, Gnatenco C, and Peterson DA (2003) Neurogenesis and brain injury: managing a renewable resource for repair. J Clin Investig 112: 1128-1133.[CrossRef][Medline]
Harvey JA (2004) Cocaine effects on the developing brain: current status. Neurosci Biobehav Rev 27: 751-764.[CrossRef][Medline]
Hauser KF, Houdi AA, Turbek CS, Elde RP, and Maxson W 3rd (2000) Opioids intrinsically inhibit the genesis of mouse cerebellar granule neuron precursors in vitro: differential impact of mu and delta receptor activation on proliferation and neurite elongation. Eur J Neurosci 12: 1281-1293.[CrossRef][Medline]
He J, Nixon K, Shetty AK, and Crews FT (2005) Chronic alcohol exposure reduces hippocampal neurogenesis and dendritic growth of newborn neurons. Eur J Neurosci 21: 2711-2720.[CrossRef][Medline]
Jakel RJ, Schneider BL, and Svendsen CN (2004) Using human neural stem cells to model neurological disease. Nat Rev Genet 5: 136-144.[CrossRef][Medline]
Johnson JE Jr and Weissman AD (1988) Cocaine produces fine structural nuclear alterations in cultured neuroglioblastoma cells. Brain Res Bull 20: 39-47.[CrossRef][Medline]
Kempermann G (2002) Why new neurons? Possible functions for adult hippocampal neurogenesis. J Neurosci 22: 635-638.
Khurdayan VK, Buch S, El-Hage N, Lutz SE, Goebel SM, Singh IN, Knapp PE, Turchan-Cholewo J, Nath A, and Hauser KF (2004) Preferential vulnerability of astroglia and glial precursors to combined opioid and HIV-1 Tat exposure in vitro. Eur J Neurosci 19: 3171-3182.[CrossRef][Medline]
Kippin TE, Kapur S, and van der Kooy D (2005) Dopamine specifically inhibits forebrain neural stem cell proliferation, suggesting a novel effect of antipsychotic drugs. J Neurosci 25: 5815-5823.
Krathwohl MD and Kaiser JL (2004) HIV-1 promotes quiescence in human neural progenitor cells. J Infect Dis 190: 216-226.[CrossRef][Medline]
Lester BM, Tronick EZ, LaGasse L, Seifer R, Bauer CR, Shankaran S, Bada HS, Wright LL, Smeriglio VL, Lu J, et al. (2002) The maternal lifestyle study: effects of substance exposure during pregnancy on neurodevelopmental outcome in 1-month-old infants. Pediatrics 110: 1182-1192.
Lidow MS and Song ZM (2001) Primates exposed to cocaine in utero display reduced density and number of cerebral cortical neurons. J Comp Neurol 435: 263-275.[CrossRef][Medline]
Mandyam CD, Norris RD, and Eisch AJ (2004) Chronic morphine induces premature mitosis of proliferating cells in the adult mouse subgranular zone. J Neurosci Res 76: 783-794.[CrossRef][Medline]
Mayes LC (1999) Developing brain and in utero cocaine exposure: effects on neural ontogeny. Dev Psychopathol 11: 685-714.[CrossRef][Medline]
McKay R (1997) Stem cells in the central nervous system. Science (Wash DC) 276: 66-71.
Nassogne MC, Louahed J, Evrard P, and Courtoy PJ (1997) Cocaine induces apoptosis in cortical neurons of fetal mice. J Neurochem 68: 2442-2450.[Medline]
Ni HT, Hu S, Sheng WS, Olson JM, Cheeran MC, Chan AS, Lokensgard JR, and Peterson PK (2004) High-level expression of functional chemokine receptor CXCR4 on human neural precursor cells. Brain Res Dev Brain Res 152: 159-169.[Medline]
Nunes MC, Roy NS, Keyoung HM, Goodman RR, McKhann G 2nd, Jiang L, Kang J, Nedergaard M, and Goldman SA (2003) Identification and isolation of multipotential neural progenitor cells from the subcortical white matter of the adult human brain. Nat Med 9: 439-447.[CrossRef][Medline]
Persson AI, Thorlin T, Bull C, Zarnegar P, Ekman R, Terenius L, and Eriksson PS (2003) Mu- and delta-opioid receptor antagonists decrease proliferation and increase neurogenesis in cultures of rat adult hippocampal progenitors. Eur J Neurosci 17: 1159-1172.[CrossRef][Medline]
Peterson DA (2002) Stem cells in brain plasticity and repair. Curr Opin Pharmacol 2: 34-42.[CrossRef][Medline]
Piper DR, Mujtaba T, Rao MS, and Lucero MT (2000) Immunocytochemical and physiological characterization of a population of cultured human neural precursors. J Neurophysiol 84: 534-548.
Powrozek TA, Sari Y, Singh RP, and Zhou FC (2004) Neurotransmitters and substances of abuse: effects on adult neurogenesis. Curr Neurovasc Res 1: 251-260.[CrossRef][Medline]
Shors TJ, Miesegaes G, Beylin A, Zhao M, Rydel T, and Gould E (2001) Neurogenesis in the adult is involved in the formation of trace memories. Nature (Lond) 410: 372-376.[CrossRef][Medline]
Singer LT, Arendt R, Minnes S, Farkas K, Salvator A, Kirchner HL, and Kliegman R (2002) Cognitive and motor outcomes of cocaine-exposed infants. J Am Med Assoc 287: 1952-1960.
Sommer L and Rao M (2002) Neural stem cells and regulation of cell number. Prog Neurobiol 66: 1-18.[CrossRef][Medline]
Tran PB, Ren D, and Miller RJ (2005) The HIV-1 coat protein gp120 regulates CXCR4-mediated signaling in neural progenitor cells. J Neuroimmunol 160: 68-76.[CrossRef][Medline]
Uchida N, Buck DW, He D, Reitsma MJ, Masek M, Phan TV, Tsukamoto AS, Gage FH, and Weissman IL (2000) Direct isolation of human central nervous system stem cells. Proc Natl Acad Sci USA 97: 14720-14725.
Zachor D, Cherkes JK, Fay CT, and Ocrant I (1994) Cocaine differentially inhibits neuronal differentiation and proliferation in vitro. J Clin Investig 93: 1179-1185.[Medline]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
 |
 |
|
 |
 |
 |
