Striatum Of Normal Rats Research Articles

Expression of vascular endothelial growth factor-C (VEGF-C) and its receptor (VEGFR-3) in the glial reaction elicited by human mesenchymal stem cell engraftment in the normal rat brain.

To determine whether vascular endothelial growth factor-C (VEGF-C) and its receptor (VEGFR-3) are involved in the glial reaction elicited by transplanted mesenchymal stem cells (MSCs), we examined the cellular localization of VEGF-C and VEGFR-3 proteins in the striatum of adult normal rats that received bone marrow-derived human MSCs. The MSC grafts were infiltrated with activated microglia/macrophages and astrocytes over a 2-week period post-transplantation, which appeared to parallel the loss of transplanted MSCs. VEGF-C/VEGFR-3 was expressed in activated microglia/macrophages recruited to the graft site, where the induction of VEGF-C protein was rather late compared with that of its receptor. VEGF-C protein was absent or very weak on day 3, whereas VEGFR-3 immunoreactivity was evident within the first three days. Furthermore, within three days, VEGF-C could be detected in the brain macrophages localized immediately adjacent to the needle track. At the same time, almost all the brain macrophages in both regions expressed VEGFR-3. Reactive astrocytes at the graft site expressed VEGFR-3, but not VEGF-C. These data demonstrated the characteristic time- and cell-dependent expression patterns for VEGF-C and VEGFR-3 within the engrafted brain tissue, suggesting that they may contribute to neuroinflammation in MSC transplantation, possibly through the recruitment and/or activation of microglia/macrophages and astrogliosis.

Synthesis and Biological Evaluation of 10‐11C‐Dihydrotetrabenazine as a Vesicular Monoamine Transporter 2 Radioligand

In this study, we synthesized a new carbon-11-labeled radiotracer, 10-(11) C-dihydrotetrabenazine (10-(11) C-DTBZ), and evaluated its potential as a vesicular monoamine transporter 2 (VMAT2) radioligand. The radiolabeled precursor 10-O-desmethyl-dihydrotetrabenazine (10-O-desmethyl-DTBZ) was prepared with a six-step reaction using 3-methoxy-4-benzyloxybenzaldehyde as starting material. 10-(11) C-DTBZ was synthesized by heating 1.0 mg of 10-hydroxy precursor and (11) C-methyl iodide in the presence of 0.3 mL of dimethyl sulfoxide and 4.0 µL of 3 N KOH at room temperature for 3 min. After purification by solid phase extraction using an alumina Sep-Pak cartridge, the final 10-(11) C-DTBZ product was obtained with a radiochemical purity of >99% and an uncorrected radiochemical yield of 18-26% (end of bombardment (EOB), n = 6). The overall synthesis time was approximately 20 min from the EOB to release of the product for quality control. Using small-animal positron emission tomography (microPET), the striatum of normal rats was found to exhibit symmetrical labeling (STR /STL = 0.98 ± 0.05, n = 3) and the highest uptake of radioactivity (striatum/cerebellum, ST/CB = 2.89 ± 0.31 at 30-60 min, n = 3). In contrast, rats with 6-hydroxydopamine unilateral lesions yielded asymmetrical striatal images with a higher 10-(11) C-DTBZ concentration on the unlesioned side (STunlesioned /CB = 2.53 ± 0.18, at 30-60 min, n = 3) compared with the lesioned side (STlesioned /CB = 1.26 ± 0.10, n = 3). These results suggest that 10-(11) C-DTBZ may represent a promising PET radiotracer for imaging VMAT2.

Similar effects of substance P on learning and memory function between hippocampus and striatal marginal division.

Substance P is an endogenous neurokinin that is present in the central and peripheral nervous systems. The neuropeptide substance P and its high-affinity receptor neurokinin 1 receptor are known to play an important role in the central nervous system in inflammation, blood pressure, motor behavior and anxiety. The effects of substance P in the hippocampus and the marginal division of the striatum on memory remain poorly understood. Compared with the hippocampus as a control, immunofluorescence showed high expression of the substance P receptor, neurokinin 1, in the marginal division of the striatum of normal rats. Unilateral or bilateral injection of an antisense oligonucleotide against neurokinin 1 receptor mRNA in the rat hippocampus or marginal division of the striatum effectively reduced neurokinin 1 receptor expression. Independent of injection site, rats that received this antisense oligonucleotide showed obviously increased footshock times in a Y-maze test. These results indicate that the marginal division of the striatum plays a similar function in learning and memory to the hippocampus, which is a valuable addition to our mechanistic understanding of the learning and memory functions of the marginal division of the striatum.

Redirection of doublecortin-positive cell migration by over-expression of the chemokines MCP-1, MIP-1α and GRO-α in the adult rat brain

Inflammation-induced chemoattraction plays a major role in adult subventricular zone (SVZ)-derived precursor cell migration following neural cell loss, in particular through the release of chemokines by activated microglia and macrophages. We previously demonstrated that monocyte chemotactic protein-1 (MCP-1) (chemokine (c-c motif) ligand (CCL)2), macrophage inflammatory protein-1α (MIP-1α) (CCL3) and growth regulatory protein-α (GRO-α) (chemokine (c-x-c motif) ligand (CXCL)1) are up-regulated following neural cell loss in the adult striatum and act as potent chemoattractants for SVZ-derived precursor cells in vitro. Based on these observations, the current study aimed to examine the individual effect of MCP-1, MIP-1α and GRO-α on the migration of adult SVZ-derived neural precursor cells in vivo. To address this without the confounding effects of injury-induced chemotactic cues, adeno-associated viral (AAV)2-mediated in vivo gene transfer was used to ectopically express either MCP-1, MIP-1α or GRO-α, or the control red fluorescent protein (RFP) in the normal adult rat striatum. The extent of doublecortin (Dcx)-positive cell recruitment from the SVZ into the striatal parenchyma was then determined at 4 and 8weeks following AAV2 injection. Ectopic expression either of MCP-1 or MIP-1α in the normal adult rat brain significantly increased the number of Dcx-positive cells and the extent of their migration into the striatum at both 4 and 8weeks after vector injection but did not promote either precursor cell proliferation or neural differentiation. In contrast, while over-expression of GRO-α 4weeks after vector injection induced a significant increase in Dcx-positive cell migration compared to control, this effect was reduced to control levels by 8weeks post injection. Further, direct comparison between MCP-1, MIP-1α and GRO-α at both 4 and 8weeks post vector injection indicated that GRO-α may have a reduced effect in inducing Dcx-positive cell migration when compared to MCP-1. Combined, these results confirm that over-expression of the chemokines MCP-1, MIP-1α and GRO-α can override cues directing precursor cell migration along the rostral migratory stream (RMS) and provides a mechanism by which neural precursor cell migration can be redirected into a non-neurogenic region. Differences in the migratory effect observed between individual chemokine may be due to ligand-binding affinity and/or receptor expression on SVZ-derived precursor cells.

Evaluation of Doxorubicin-Loaded 3-Helix Micelles as Nanocarriers

Designing stable drug nanocarriers, 10-30 nm in size, would have significant impact on their transport in circulation, tumor penetration, and therapeutic efficacy. In the present study, biological properties of 3-helix micelles loaded with 8 wt % doxorubicin (DOX), ~15 nm in size, were characterized to validate their potential as a nanocarrier platform. DOX-loaded micelles exhibited high stability in terms of size and drug retention in concentrated protein environments similar to conditions after intravenous injections. DOX-loaded micelles were cytotoxic to PPC-1 and 4T1 cancer cells at levels comparable to free DOX. 3-Helix micelles can be disassembled by proteolytic degradation of peptide shell to enable drug release and clearance to minimize long-term accumulation. Local administration to normal rat striatum by convection enhanced delivery (CED) showed greater extent of drug distribution and reduced toxicity relative to free drug. Intravenous administration of DOX-loaded 3-helix micelles demonstrated improved tumor half-life and reduced toxicity to healthy tissues in comparison to free DOX. In vivo delivery of DOX-loaded 3-helix micelles through two different routes clearly indicates the potential of 3-helix micelles as safe and effective nanocarriers for cancer therapeutics.

IGF-I redirects doublecortin-positive cell migration in the normal adult rat brain

The migration of subventricular zone (SVZ)-derived neural precursor cells through the rostral migratory stream (RMS) to the olfactory bulb is tightly regulated by local micro-environmental cues. Insulin-like Growth Factor-I (IGF-I) can stimulate the migration of several neuronal cell types and acts as a ‘departure’ factor in the avian SVZ. To establish whether IGF-I can also act as a migratory factor for adult neuronal precursor cells in vivo, in addition to its well established role in precursor cell proliferation and differentiation, we used AAV2-mediated gene transfer to produce ectopic expression of IGF-I in the normal adult rat striatum. We then assessed whether the expression of IGF-I would recruit SVZ-derived neuronal precursor cells from the RMS into the striatum. Ectopic expression of IGF-I in the normal adult rat brain significantly increased the number of doublecortin (Dcx)-positive cells and the extent of their migration into the striatum 4 and 8weeks after AAV2–IGF-I injection but did not promote neuronal differentiation. In vitro migration assays confirmed that IGF-I is an inducer of migration and directs SVZ-derived adult neuronal precursor cell migration by both chemotaxis and chemokinesis. These results demonstrate that overexpression of IGF-I in the normal adult rat brain can override the normal cues directing precursor cell migration along the RMS and can redirect precursor cell migration into a non-neurogenic region. Enhanced expression of IGF-I following brain injury may therefore act as a diffusible factor mediating precursor cell migration to areas of neuronal cell damage.

Clearance and Toxicity of Recombinant Methionyl Human Glial Cell Line-Derived Neurotrophic Factor (r-metHu GDNF) Following Acute Convection-Enhanced Delivery into the Striatum

BackgroundDespite promising early results, clinical trials involving the continuous delivery of recombinant methionyl human glial cell line-derived neurotrophic factor (r-metHuGDNF) into the putamen for the treatment of Parkinson's disease have shown evidence of poor distribution and toxicity due to point-source accumulation. Convection-enhanced delivery (CED) has the potential to facilitate more widespread and clinically effective drug distribution.AimsWe investigated acute CED of r-metHuGDNF into the striatum of normal rats in order to assess tissue clearance, toxicity (neuron loss, gliosis, microglial activation, and decreases in synaptophysin), synaptogenesis and neurite-outgrowth. We investigated a range of clinically relevant infused concentrations (0.1, 0.2, 0.6 and 1.0 µg/µL) and time points (2 and 4 weeks) in order to rationalise a dosing regimen suitable for clinical translation.ResultsTwo weeks after single dose CED, r-metHuGDNF was below the limit of detection by ELISA but detectable by immunohistochemistry when infused at low concentrations (0.1 and 0.2 µg/µL). At these concentrations, there was no associated neuronal loss (neuronal nuclei, NeuN, immunohistochemistry) or synaptic toxicity (synaptophysin ELISA). CED at an infused concentration of 0.2 µg/µL was associated with a significant increase in synaptogenesis (p<0.01). In contrast, high concentrations of r-metHuGDNF (above 0.6 µg/µL) were associated with neuronal and synaptic toxicity (p<0.01). Markers for gliosis (glial fibrillary acidic protein, GFAP) and microglia (ionized calcium-binding adapter molecule 1, Iba1) were restricted to the needle track and the presence of microglia had diminished by 4 weeks post-infusion. No change in neurite outgrowth (Growth associated protein 43, GAP43, mRNA) compared to artificial cerebral spinal fluid (aCSF) control was observed with any infused concentration.ConclusionThe results of this study suggest that acute CED of low concentrations of GDNF, with dosing intervals determined by tissue clearance, has most potential for effective clinical translation by optimising distribution and minimising the risk of toxic accumulation.

Increased encapsulated cell biodelivery of nerve growth factor in the brain by transposon-mediated gene transfer

Nerve growth factor (NGF) is a potential therapeutic agent for Alzheimer's disease (AD) as it has positive effects on the basal forebrain cholinergic neurons whose degeneration correlates with the cognitive decline in AD. We have previously described an encapsulated cell biodelivery device, NsG0202, capable of local delivery of NGF by a genetically modified human cell line, NGC-0295. The NsG0202 devices have shown promising safety and therapeutic results in a small phase 1b clinical study. However, results also show that the NGF dose could advantageously be increased. We have used the sleeping beauty transposon expression technology to establish a new clinical grade cell line, NGC0211, with at least 10 times higher NGF production than that of NGC-0295. To test whether encapsulation of this cell line provides a relevant dose escalation step in delivering NGF for treatment of the cognitive decline in AD patients, we have validated the bioactivity of devices with NGC0211 and NGC-0295 cells in normal rat striatum as well as in the quinolinic acid striatal lesion model. These preclinical animal studies show that implantation of devices with NGC0211 cells lead to significantly higher NGF output, which in both cases correlate with highly improved potency.

A New Technological Fusion of PET and MRI for Brain Imaging

Non-invasive imaging modalities for living animal models are a powerful research tool for the evaluation of potential drugs and treatments for human diseases. Parkinson’s disease is a neurodegenerative disorder associated with aging, and patients with this disease have a deficiency of dopaminergic neurons. In the study, we evaluated fusion imaging with positron emission tomography (PET) and magnetic resonance imaging (MRI) in the rat brain with [ 18 F]FP-CIT which binds with high affinity to dopamine transporters. PET and MRI fusion images were well registered with conventional Inveon Research Workplace software, even though they are different modalities. In PET/MRI fusion images, we showed that the uptake of [ 18 F]FP-CIT was clearly increased in the normal rat striatum and these images accurately matched the morphology in the rat brain atlas. PET/MRI images easily and accurately identified the regions of interest in the target tissue compared to PET/CT images and enabled us to calculate the uptake of the PET tracer. Therefore, combined PET/MRI analysis provides functional and anatomical information for studying biology and pathology in preclinical research.

Striatal adenosine A2A receptor-mediated positron emission tomographic imaging in 6-hydroxydopamine-lesioned rats using [18F]-MRS5425

A(2A) receptors are expressed in the basal ganglia, specifically in striatopallidal GABAergic neurons in the striatum (caudate-putamen). This brain region undergoes degeneration of presynaptic dopamine projections and depletion of dopamine in Parkinson's disease. We developed an (18)F-labeled A(2A) analog radiotracer ([(18)F]-MRS5425) for A(2A) receptor imaging using positron emission tomography (PET). We hypothesized that this tracer could image A(2A) receptor changes in the rat model for Parkinson's disease, which is created following unilateral injection of the monoaminergic toxin 6-hydroxydopamine (6-OHDA) into the substantia nigra. [(18)F]-MRS5425 was injected intravenously in anesthetized rats, and PET imaging data were collected. Image-derived percentage injected doses per gram (%ID/g) in regions of interest was measured in the striatum of normal rats and in rats unilaterally lesioned with 6-OHDA after intravenous administration of saline (baseline), D(2) agonist quinpirole (1.0 mg/kg) or D(2) antagonist raclopride (6.0 mg/kg). Baseline %ID/g reached a maximum at 90 s and maintained plateau for 3.5 min, and then declined slowly thereafter. In 6-OHDA-lesioned rats, %ID/g was significantly higher in the lesioned side compared to the intact side, and the baseline total %ID/g (data from both hemispheres were combined) was significantly higher compared to quinpirole stimulation starting from 4.5 min until the end of acquisition at 30 min. Raclopride did not produce any change in uptake compared to baseline or between the hemispheres. Thus, increase of A(2A) receptor-mediated uptake of radioactive MRS5425 could be a superior molecular target for Parkinson's imaging.

Intrastriatal grafts of mesenchymal stem cells in adult intact rats can elevate tyrosine hydroxylase expression and dopamine levels

MSCs (mesenchymal stem cells) derived from the bone marrow have shown to be a promising source of stem cells in a therapeutic strategy of neurodegenerative disorder. Also, MSCs can enhance the TH (tyrosine hydroxylase) expression and DA (dopamine) content in catecholaminergic cells by in vitro co-culture system. In the present study, we investigated the effect of intrastriatal grafts of MSCs on TH protein and gene levels and DA content in adult intact rats. When MSCs were transplanted into the striatum of normal rats, the grafted striatum not only had significantly higher TH protein and mRNA levels, but also significantly higher DA content than the untransplanted striatum. Meanwhile, the grafted MSCs differentiated into neurons, astrocytes and oligodendrocytes; however, TH-positive cells could not be detected in our study. These experimental results offer further evidence that MSCs are a promising candidate for treating neurodegenerative diseases such as Parkinson's disease.

The Ca2+ activated SK3 channel is expressed in microglia in the rat striatum and contributes to microglia-mediated neurotoxicity in vitro

BackgroundSmall-conductance Ca2+ activated K+ channels are expressed in the CNS, where KCNN2/SK2/KCa2.2 and KCNN3/SK3/KCa2.3 help shape the electrical activity of some neurons. The SK3 channel is considered a potential therapeutic target for diseases and disorders involving neuron hyper-excitability but little is known about its expression and roles in non-neuronal cells in either the healthy or damaged CNS. The purpose of this study was to examine expression of KCNN3/SK3 in CNS microglia in vivo and in vitro, and to use an established in vitro model to determine if this channel contributes to the neurotoxic capacity of activated microglia.MethodsKCNN3 mRNA (real-time RT-PCR) and SK3 immunoreactivity were examined in rat microglia. Lipopolysaccharide was then used to activate microglia (monitored by iNOS, nitric oxide, activation of NF-κB and p38 MAPK) and transform them to a neurotoxic state. Microglia-mediated neuron damage (TUNEL, activated caspase 3) and nitrotyrosine levels were quantified using a two-chamber system that allowed microglia to be treated with channel blockers, washed and then added to neuron/astrocyte cultures. Contributions of SK3 to these processes were discriminated using a subtractive pharmacological approach with apamin and tamapin. ANOVA and post-hoc tests were used to assess the statistical significance of differences between treatment groups. SK3 immunoreactivity was then compared in the normal and damaged adult rat striatum, by injecting collagenase (a hemorrhagic stroke) or endothelin-1 (a transient ischemic stroke).ResultsKCNN3 mRNA was prevalent in cultured microglia and increased after lipopolysaccharide-induced activation; SK3 channel blockade inhibited microglial activation and reduced their ability to kill neurons. SK3 immunoreactivity was prevalent in cultured microglia and throughout the adult rat striatum (except white matter tracts). After strokes, SK3 was highly expressed in activated microglia/macrophages within the lesions, but reduced in other cells.ConclusionsSK3 is expressed in microglia in both the healthy and damaged adult striatum, and mechanistic in vitro studies show it contributes to transformation of microglia to an activated neurotoxic phenotype. Thus, SK3 might be a therapeutic target for reducing inflammation-mediated acute CNS damage. Moreover, its roles in microglia must be considered when targeting this channel for CNS diseases, disorders and reducing neuron hyper-excitability.

Alterations in AMPA receptor phosphorylation in the rat striatum following acute and repeated cocaine administration

Protein phosphorylation is an important mechanism for the posttranslational modulation of ionotropic glutamate receptors and is subject to regulation by changing synaptic inputs. In this study, we investigated the regulation of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor GluR1 subunit phosphorylation by cocaine exposure in the rat dorsal striatum in vivo. We found that acute cocaine challenge followed by 6 days of repeated systemic injections of cocaine (20 mg/kg once daily) enhanced the sensitivity of the GluR1 subunit in its phosphorylation at serine 831 (Ser831) in the dorsal striatum. This enhancement of the sensitivity of Ser831 phosphorylation was reduced, at the receptor and ion channel level, by blocking (1) group I metabotropic glutamate receptors (mGluRs), (2) N-methyl- d-aspartate receptors, and (3) L-type voltage-operated Ca 2+ channels. Similar reduction of the enhancement was also induced, at the protein kinase level, by inhibiting (1) protein kinase C, (2) calcium/calmodulin-dependent protein kinases, and (3) c-Jun N-terminal kinases. In addition, inhibition of protein phosphatase 1/2A or calcineurin increased GluR1-Ser831 phosphorylation in the dorsal striatum of normal rats, whereas inhibition of these phosphatases did not further enhance the Ser831 phosphorylation in rats pretreated with 7 daily injections of cocaine. These data suggest that the phosphorylation of AMPA receptor GluR1 subunits at Ser831 is subject to upregulation by acute and repeated cocaine administration. Complex signaling integrations among glutamate receptors, Ca 2+ channels, protein kinases, and protein phosphatases participate in this upregulation.

The Ca2+ activated SK3 channel is expressed in microglia in the rat striatum and contributes to microglia-mediated neurotoxicity in vitro

Event Abstract Back to Event The Ca2+ activated SK3 channel is expressed in microglia in the rat striatum and contributes to microglia-mediated neurotoxicity in vitro Lyanne C. Schlichter1, Vikas Kaushal1, Iska Moxon-Emre1, Vishanthan Sivagnanam1 and Catherine Vincent1* 1 Toronto Western Research Institute, University Health Network, Department of Physiology, Canada Background Small-conductance Ca2+ activated K+ channels are expressed in the CNS, where KCNN2/SK2/KCa2.2 and KCNN3/SK3/KCa2.3 help shape the electrical activity of some neurons. The SK3 channel is considered a potential therapeutic target for diseases and disorders involving neuron hyper-excitability but little is known about its expression and roles in non-neuronal cells. The purpose of this study was to examine SK3 expression in CNS microglia in vivo and in vitro, and to use an established in vitro model to determine if this channel contributes to the neurotoxicity of activated microglia. Methods KCNN3 mRNA (real-time RT-PCR) and SK3 immunoreactivity were examined in rat microglia. Lipopolysaccharide (LPS) was used to activate microglia (monitored by iNOS, nitric oxide, activation of NF-κB and p38 MAPK) and transform them to a neurotoxic state. Microglia-mediated neuron damage (TUNEL, activated caspase-3, tyrosine nitration) was assessed using a two-chamber system that allowed microglia to be treated with channel blockers, washed and then added to neuron/astrocyte cultures. Contributions of SK3 to these processes were discriminated using a subtractive pharmacological approach with apamin and tamapin. SK3 immunoreactivity was then compared in the normal and damaged adult rat striatum, by injecting collagenase (hemorrhagic stroke) or endothelin-1 (transient ischemic stroke). Results KCNN3 mRNA was prevalent in cultured microglia and increased after LPS-induced activation; SK3 blockers inhibited microglia activation and reduced their ability to kill neurons. SK3 immunoreactivity was prevalent in cultured microglia and throughout the adult rat striatum (except white matter tracts). After strokes, SK3 was highly expressed in activated microglia/macrophages within the lesions and reduced in other cells. Conclusions SK3 is expressed in microglia in both healthy and damaged adult striatum, and mechanistic in vitro studies show it contributes to transformation of microglia to an activated neurotoxic phenotype. Thus, SK3 might be a therapeutic target for reducing inflammation-mediated acute CNS damage. Conference: B.R.A.I.N. platform in Physiology poster day 2009, Toronto, ON, Canada, 16 Dec - 16 Dec, 2009. Presentation Type: Poster Presentation Topic: Poster presentations Citation: Schlichter LC, Kaushal V, Moxon-Emre I, Sivagnanam V and Vincent C (2009). The Ca2+ activated SK3 channel is expressed in microglia in the rat striatum and contributes to microglia-mediated neurotoxicity in vitro. Front. Neurosci. Conference Abstract: B.R.A.I.N. platform in Physiology poster day 2009. doi: 10.3389/conf.neuro.03.2009.17.056 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Dec 2009; Published Online: 18 Dec 2009. * Correspondence: Catherine Vincent, Toronto Western Research Institute, University Health Network, Department of Physiology, Toronto, Canada, cat.vincent@utoronto.ca Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Lyanne C Schlichter Vikas Kaushal Iska Moxon-Emre Vishanthan Sivagnanam Catherine Vincent Google Lyanne C Schlichter Vikas Kaushal Iska Moxon-Emre Vishanthan Sivagnanam Catherine Vincent Google Scholar Lyanne C Schlichter Vikas Kaushal Iska Moxon-Emre Vishanthan Sivagnanam Catherine Vincent PubMed Lyanne C Schlichter Vikas Kaushal Iska Moxon-Emre Vishanthan Sivagnanam Catherine Vincent Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Dopaminergic but Not Glutamatergic Neurotransmission Is Increased in the Striatum after Selective Cyclooxygenase‐2 Inhibition in Normal and Hemiparkinsonian Rats

In the present work, we studied the effect of the selective cyclooxygenase-2 (COX-2) inhibitors, compound 11 g, celecoxib and selective COX-1 inhibitor SC-560 (intraperitoneally and acutely) on striatal glutamatergic and dopaminergic neurotransmission in normal and substantia nigra pars compacta (SNc)-lesioned rats using the microdialysis technique. We also investigated the effect of acute COX inhibition on the damaged SNc neurons. Our results indicate a significant increase in dopaminergic neurotransmission and a decrease in glutamatergic neurotransmission (P<0.05) only after selective COX-2 inhibition in the striatum of normal and hemiparkinsonian rats. Nonetheless, neither COX-1 nor COX-2 inhibitors showed any improvement in the damaged SNc neurons.

Disparate Host Response and Donor Survival After the Transplantation of Mesenchymal or Neuroectodermal Cells to the Intact Rodent Brain

To circumvent ethical and legal complications associated with embryonic cell sources, investigators have proposed the use of nonneural donor sources for use in neural transplantation strategies. Leading candidate sources include autologous marrow stromal cells (MSCs) and fibroblasts, which are mesodermal derivatives. However, we recently reported that MSCs transplanted to the adult brain are rapidly rejected by an inflammatory response. Whether extrinsic variables or intrinsic mesenchymal traits stimulated inflammation and rejection is unknown. To determine the future utility of these cells in neural transplantation, we have now performed a systematic analysis of MSC transplantation to the brain. To examine the effects of extrinsic variables on transplantation, green fluorescent protein (GFP)-expressing rat MSCs, cultured under distinct conditions, were transplanted stereotactically to the normal adult rat striatum, and donor survival and the host response was compared. To examine whether intrinsic donor traits promoted rejection, 50,000 GFP-expressing rat MSCs, fibroblasts, or astrocytes were transplanted stereotactically to the adult rat striatum and graft survival and the host response was compared. Irrespective of preoperative culture conditions, MSCs elicited an inflammatory response and were rejected by 14 days, indicating acute rejection was not mediated by culture conditions. Comparison of MSC, fibroblast, or astrocyte grafts revealed that mesenchymal derivatives, MSCs and fibroblasts, elicited an inflammatory response and were rapidly rejected, whereas neuroectodermal astrocytes demonstrated robust survival in the absence of inflammation. Our findings suggest that intrinsic characteristics of mesenchymal cells may stimulate host inflammation, and thus may not represent an ideal donor source for transplantation to the adult brain.

Creating a neurogenic environment: The role of BDNF and FGF2

Regional environmental cues present in the adult brain determine the fate of adult neural progenitor cells. To determine whether the growth factors BDNF or FGF2 can create a neurogenic environment outside the SVZ, we used AAV1/2-mediated gene transfer to produce ectopic BDNF or FGF2 expression in the normal adult rat striatum and transplanted SVZ-derived progenitor cells into this region. We observed that ectopic expression of BDNF in the striatum promoted neuronal differentiation of transplanted adult neural progenitor cells, while FGF2 expression supported the survival and proliferation of transplanted progenitor cells in the adult striatum. However, region-specific neuronal differentiation of transplanted progenitor cells was not observed in the adult striatum, suggesting ectopic BDNF or FGF2 expression was insufficient for the generation of mature neuronal phenotypes. This study provides direct in vivo evidence that ectopic striatal expression of either BDNF or FGF2 can induce neurogenesis in non-neurogenic regions of the adult brain.

Dual‐modality in vivo monitoring of subventricular zone stem cell migration and metabolism

Rat subventricular zone (SVZ) stem cells were labeled with superparamagnetic iron oxide particles (SPIO) to follow their fate and migratory potential with magnetic resonance imaging (MRI) and positron emission tomography (PET). Labeled cells were transplanted into either the right rostral migratory stream (RMS) or striatum of normal adult Sprague-Dawley rats and serially followed for 3 months. Minimal migration of the cells implanted into the striatum was observed after 3 weeks whereas SVZ cells implanted into the RMS migrated toward the olfactory bulb at 1 week post-transplantation. PET studies of glucose metabolism using (18)F-FDG demonstrated enhanced glucose utilization in the striatum of transplanted animals. PET studies conducted 3 months after transplantation showed elevated accumulation of (11)C-raclopride (dopamine receptor type 2) and (11)C-CFT (dopamine transporter) binding in the striatal grafts. Implanted SVZ cells did not induce significant inflammation as identified by PET using (11)C-PK11195, a ligand detecting activated microglia. Histological analysis identified viable SPIO-labeled cells (some of which were nestin-positive) 7 weeks post-transplantation, suggesting a prolonged presence of undifferentiated neural stem cells within transplants. In addition, double immunostaining for neuronal and astrocytic markers (NeuN and GFAP) indicated that differentiation into neuronal and astrocytic phenotypes also occurred. Thus, combining MRI and PET enables monitoring of cell migration and metabolism non-invasively in vivo for extended periods of time.

Blueberry- and spirulina-enriched diets enhance striatal dopamine recovery and induce a rapid, transient microglia activation after injury of the rat nigrostriatal dopamine system

Neuroinflammation plays a critical role in loss of dopamine neurons during brain injury and in neurodegenerative diseases. Diets enriched in foods with antioxidant and anti-inflammatory actions may modulate this neuroinflammation. The model of 6-hydroxydopamine (6-OHDA) injected into the dorsal striatum of normal rats, causes a progressive loss of dopamine neurons in the ventral mesencephalon. In this study, we have investigated the inflammatory response following 6-OHDA injected into the striatum of adult rats treated with diet enriched in blueberry or spirulina. One week after the dopamine lesion, a similar size of dopamine degeneration was found in the striatum and in the globus pallidus in all lesioned animals. At 1 week, a significant increase in OX-6- (MHC class II) positive microglia was found in animals fed with blueberry- and spirulina-enriched diets in both the striatum and the globus pallidus. These OX-6-positive cells were located within the area of tyrosine hydroxylase (TH) -negativity. At 1 month after the lesion, the number of OX-6-positive cells was reduced in diet-treated animals while a significant increase beyond that observed at 1 week was now present in lesioned control animals. Dopamine recovery as revealed by TH-immunohistochemistry was significantly enhanced at 4 weeks postlesion in the striatum while in the globus pallidus the density of TH-positive nerve fibers was not different from control-fed lesioned animals. In conclusion, enhanced striatal dopamine recovery appeared in animals treated with diet enriched in antioxidants and anti-inflammatory phytochemicals and coincided with an early, transient increase in OX-6-positive microglia.

Susceptibility of striatal neurons to excitotoxic injury correlates with basal levels of Bcl-2 and the induction of P53 and c-Myc immunoreactivity

The present studies evaluated the potential contribution of Bcl-2, p53, and c-Myc to the differential vulnerability of striatal neurons to the excitotoxin quinolinic acid (QA). In normal rat striatum, Bcl-2 immunoreactivity (Bcl-2-i) was most intense in large aspiny interneurons including choline acetyltransferase positive (CAT+) and parvalbumin positive (PARV+) neurons, but low in a majority of medium-sized neurons. In human brain, intense Bcl-2-i was seen in large striatal neurons but not in medium-sized spiny projection neurons. QA produced degeneration of numerous medium-sized neurons, but not those enriched in Bcl-2-i. Many Bcl-2-i-enriched interneurons including those with CAT+ and PARV+ survived QA injection, while medium-sized neurons labeled for calbindin D-28K (CAL D-28+) did not. In addition, proapoptotic proteins p53-i and c-Myc-i were robustly induced in medium-sized neurons, but not in most large neurons. The selective vulnerability of striatal medium spiny neurons to degeneration in a rodent model of Huntington's disease appears to correlate with their low levels of Bcl-2-i and high levels of induced p53-i and c-Myc-i.