Alpha-synuclein aggregates are phosphatase resistant

Alpha-synuclein (αsyn) is an intrinsically disordered protein that aggregates in the brain in several neurodegenerative diseases collectively called synucleinopathies. Phosphorylation of αsyn at serine 129 (PSER129) was considered rare in the healthy human brain but is enriched in pathological αsyn aggregates and is used as a specific marker for disease inclusions. However, recent observations challenge this assumption by demonstrating that PSER129 results from neuronal activity and can be readily detected in the non-diseased mammalian brain. Here, we investigated experimental conditions under which two distinct PSER129 pools, namely endogenous-PSER129 and aggregated-PSER129, could be detected and differentiated in the mammalian brain. Results showed that in the wild-type (WT) mouse brain, perfusion fixation conditions greatly influenced the detection of endogenous-PSER129, with endogenous-PSER129 being nearly undetectable after delayed perfusion fixation (30-minute and 1-hour postmortem interval). Exposure to anesthetics (e.g., Ketamine or xylazine) before perfusion did not significantly influence endogenous-PSER129 detection or levels. In situ, non-specific phosphatase calf alkaline phosphatase (CIAP) selectively dephosphorylated endogenous-PSER129 while αsyn preformed fibril (PFF)-seeded aggregates and genuine disease aggregates (Lewy pathology and Papp-Lantos bodies in Parkinson's disease and multiple systems atrophy brain, respectively) were resistant to CIAP-mediated dephosphorylation. The phosphatase resistance of aggregates was abolished by sample denaturation, and CIAP-resistant PSER129 was closely associated with proteinase K (PK)-resistant αsyn (i.e., a marker of aggregation). CIAP pretreatment allowed for highly specific detection of seeded αsyn aggregates in a mouse model that accumulates non-aggregated-PSER129. We conclude that αsyn aggregates are impervious to phosphatases, and CIAP pretreatment increases detection specificity for aggregated-PSER129, particularly in well-preserved biological samples (e.g., perfusion fixed or flash-frozen mammalian tissues) where there is a high probability of interference from endogenous-PSER129. Our findings have important implications for the mechanism of PSER129-accumulation in the synucleinopathy brain and provide a simple experimental method to differentiate endogenous-from aggregated PSER129.

Health Economic Considerations in the Deployment of an Alzheimer's Prevention Therapy

INTRODUCTION

As treatments for secondary prevention of Alzheimer's disease (AD) are being studied, concerns about their value for money have appeared. We estimate cost-effectiveness of a hypothetical screening and prevention program.

METHODS

We use a Markov model to project cost-effectiveness of a treatment that reduces progression to symptomatic AD by 50% with either chronic treatment until progression to mild cognitive impairment or treatment for one year followed by monitoring with AD blood tests and retreatment with one dose in case of amyloid re-accumulation. Diagnoses would be made with an AD blood test with sensitivity and specificity of 80%, and inconclusive results in 20%. Individuals testing negative would be re-tested in five years and those with inconclusive results in one.

RESULTS

The program would generate per-person value of $53,721 from a payer (reduction of direct cost and patient QALY gains) and $69,861 from a societal perspective (adding valuation of reduced caregiver burden). With chronic treatment, it would be cost-effective up to annual drug prices of $7,000 and $10,300, respectively. Time-limited treatment would be cost-effective at annual drug prices of $54,257 and $78,458 from a payer and societal perspective, respectively. Higher specificity of the blood test would decrease cost per person with similar value generation DISCUSSION: A hypothetical prevention treatment for AD could be economically viable from a payer and societal perspective.

In utero Exposure to Anesthetics Alters Neuronal Migration Pattern in Developing Cerebral Cortex and Causes Postnatal Behavioral Deficits in Rats

During fetal development, cerebral cortical neurons are generated in the proliferative zone along the ventricles and then migrate to their final positions. To examine the impact of in utero exposure to anesthetics on neuronal migration, we injected pregnant rats with bromodeoxyuridine to label fetal neurons generated at embryonic Day (E) 17 and then randomized these rats to 9 different groups receiving 3 different means of anesthesia (oxygen/control, propofol, isoflurane) for 3 exposure durations (20, 50, 120 min). Histological analysis of brains from 54 pups revealed that significant number of neurons in anesthetized animals failed to acquire their correct cortical position and remained dispersed within inappropriate cortical layers and/or adjacent white matter. Behavioral testing of 86 littermates pointed to abnormalities that correspond to the aberrations in the brain areas that are specifically developing during the E17. In the second set of experiments, fetal brains exposed to isoflurane at E16 had diminished expression of the reelin and glutamic acid decarboxylase 67, proteins critical for neuronal migration. Together, these results call for cautious use of anesthetics during the neuronal migration period in pregnancy and more comprehensive investigation of neurodevelopmental consequences for the fetus and possible consequences later in life.

Neural Transplantation of Cells Expressing the Anti-Apoptotic Gene Bcl-2

Long-term survival of grafted neural cells is a major goal of neural transplantation, but typical survival rates of grafted fetal neurons are in the range of 5-10%. Whether the death of transplanted neural cells is apoptotic or necrotic is unknown. The expression of the proto-oncogene bcl-2 inhibits both apoptotic and necrotic neural cell death. In a 6-OHDA induced rat model of Parkinson's disease, Hoechst 33258 prelabelled conditionally immortalized nigral cells engineered to express bcl-2 were stereotactically transplanted into the striatum ipsilaterally to the lesioned nigrostriatal pathway. Sixteen rats received bcl-2 transfected cells, 15 received cells transfected with vector alone, and 12 received either a nondopaminergic cell line or were sham transplanted as controls. Four wk following transplantation, the rats with grafts containing bcl-2 expressing cells showed an approximately 43% decrease in apomorphine-induced rotational behavior. In contrast, 12% improvement occurred in the rats with transplanted cells transfected with vector alone (p < 0.05), and no improvement occurred in sham-operated animals (p < 0.05). Histological examination showed no tumor formation. Despite the difference in behavioral effect, no clear difference in Hoechst fluorescent staining or staining for TH, GFAP was noted; therefore, it is unknown at present whether the observed effect was due to a difference in survival or to increased efficacy per surviving transplanted neural cell, or both.

Long-Term Viability of Isolated Bovine Adrenal Medullary Chromaffin Cells following Intrastriatal Transplantation

Adrenal medullary grafts generally exhibit poor viability when grafted into the striatum. Previous work in our laboratory demonstrated that chromaffin cells can survive well for up to 2 mo following grafting into the intact rat striatum after cells are isolated from the nonchromaffin supporting cells (fibroblasts and endothelial cells) of the adrenal medulla. The aim of the present study was to assess the long-term viability of isolated bovine chromaffin cells following grafting into the intact rat striatum. The viability of grafted bovine adrenal medullary chromaffin cells was compared in rats receiving either (a) perfused adrenal medulla; (b) isolated chromaffin cells; or (c) isolated chromaffin cells that were subsequently recombined with their nonchromaffin supporting cells. One year postimplantation, all graft types which included fibroblasts and endothelial cells were infiltrated with macrophages and demonstrated an abundance of cellular debris. No viable chromaffin cells were observed. In contrast, healthy tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DβH) immunoreactive chromaffin cells survived for 1 yr posttransplantation when grafted in isolation from the nonchromaffin constituents of the adrenal medulla. Good xenograft survival was achieved in this group despite the fact that these rats were only immunosuppressed for 1 mo postimplantation. Grafted cells demonstrated morphological characteristics of chromaffin cells in situ and these implants were not accompanied by macrophage infiltration. These data demonstrate that long-term survival of chromaffin cells can be achieved following intrastriatal implantation and the viability of grafted chromaffin cells is dependent upon the removal of the nonchromaffin supporting cells.

The Influence of Donor Age on the Survival of Solid and Suspension Intraparenchymal Human Embryonic Nigral Grafts

In many species, graft survival and graft-derived behavioral recovery are affected by the embryonic donor age. We compared the ability of solid and suspension grafts of human embryonic mesencephalic dopaminergic (DA) neurons at different embryonic stages to survive intra-parenchymal transplantation into 6-OHDA lesioned immunosuppressed rats. Suspension grafts survived best when donor age was between postconception (PC) days 34 and 56. Transplants displayed numerous healthy tyrosine hydroxylase immunoreactive (TH-IR) neurons which sent extensive neuritic processes into the host striatum. Suspension grafts survived poorly when donor age was greater than 65 days. Solid implants displayed comparable viability of TH-IR neurons when donor age was between 44 and 65 days. No solid grafts contained TH-IR cells when donor tissue was older than 72 days. The suspension and solid methods of transplantation resulted in comparable survival of robust grafts, but solid grafts resulted in more intergraft variability than suspension grafts, particularly among the more marginal implants. Our results demonstrate that the upper limit for survival of human embryonic DA suspension grafts correlates well with the period of development of the human nigrostriatal pathway. The “window” for donor age of solid human embryonic DA grafts appears to be extended by about 9 days in comparison to suspension grafts. These data suggest that the upper age limit for grafting human mesencephalic DA neurons should be PC day 56 for suspension grafts, and PC day 65 for solid implants. Older donors are likely to produce grafts with fewer surviving DA neurons.

Cellular Delivery of Cntf but not Nt-4/5 Prevents Degeneration of Striatal Neurons in a Rodent Model of Huntington's Disease

The delivery of neurotrophic factors to the central nervous system (CNS) has gained considerable attention as a potential treatment strategy for neurodegenerative disorders such as Huntington's disease (HD). In the present study, we directly compared the ability of two neurotrophic factors, ciliary neurotrophic factor (CNTF), and neurotrophin-4/5 (NT-4/5), to prevent the degeneration of striatal neurons following intrastriatal injections of quinolinic acid (QA). Expression vectors containing either the human CNTF or NT-4/5 gene were transfected into a baby hamster kidney fibroblast cell line (BHK). Using a polymeric device, encapsulated BHK-control cells and those secreting either CNTF (BHK-CNTF) or NT-4/5 (BHK-NT-4/5) were transplanted unilaterally into the rat lateral ventricle. Seven days later, the same animals received unilateral injections of QA (225 nmol) into the ipsilateral striatum. Nissl-stained sections demonstrated that the BHK-CNTF cells significantly reduced the volume of striatal damage produced by QA. Quantitative analysis of striatal neurons further demonstrated that both choline acetyltransferase (ChAT)- and glutamic acid decarboxylase (GAD)-immunoreactive neurons were protected by CNTF implants. In contrast, the volume of striatal damage and loss of striatal ChAT and GAD-positive neurons in animals receiving BHK-NT-4/5 implants did not differ from control-implanted animals. These results help better define the scope of neuronal protection that can be afforded following cellular delivery of various neurotrophic factors. Moreover, these data further support the concept that implants of polymer-encapsulated CNTF-releasing cells can be used to protect striatal neurons from excitotoxic damage, and that this strategy may ultimately prove relevant for the treatment of HD.

Encapsulated PC 12 Cell Transplants into Hemiparkinsonian Monkeys: A Behavioral, Neuroanatomical, and Neurochemical Analysis

Four cynomolgus monkeys were trained on a hand reaching task and then rendered hemiparkinsonian with an intracarotid injection of n-methyl 4 phenyl 1,2,3,6, tetrahydropyridine (MPTP). Performance on this task with the limb contralateral to the MPTP injection was significantly impaired following the lesion. Three monkeys received implants of polymer-encapsulated containing PC12 cells into the caudate nucleus and putamen. One monkey received identical implants of empty capsules and served as a control. After a transient improvement, limb use in the control monkey dissipated and returned to post-MPTP disability. Two of the three PC12 cell grafted monkeys recovered performance on the hand reach task to near normal levels for up to 6.5 mo posttransplantation. Capsules retrieved from the monkeys who recovered limb function postimplantation contained numerous viable PC12 cells that continued to release levodopa, basal dopamine, and potassium evoked dopamine. In contrast, capsules retrieved from the PC12 cell-grafted monkey which did not recover limb use on the hand reach task contained few cells which secreted negligible or undetectable levels of levodopa and dopamine. Interestingly, functional disability was not reinstated following removal of the capsules. Neuroanatomical and neurochemical evaluation of the grafted striatum did not reveal a host-derived sprouting response of catecholaminergic or indolaminergic fibers. These data indicate that xenografts of PC12 cells can survive for up to 6.5 mo in nonimmunosuppressed monkeys when immunoisolated via polymer encapsulation. Moreover, these cells continue to secrete high levels of levodopa and dopamine and induce recovery of motor function in parkinsonian nonhuman primates.

Fetal Grafting for Parkinson's Disease: Expression of Immune Markers in Two Patients with Functional Fetal Nigral Implants

In a number of centers throughout the world, fetal nigral transplantation is being performed for the treatment of Parkinson's disease (PD). Clinical results have been inconsistent. One parameter that differs among transplant studies is the degree and manner by which patients are immunosuppressed following transplantation. Indeed, the role of the immune system following fetal grafting in humans is not well understood. Recently, two patients from our open label trial that received fetal nigral implants have come to autopsy. These patients were immunosuppressed with cyclosporin for 6 mo posttransplantation and survived for a total of 18 mo postgrafting. Robust survival of grafted dopamine-containing cells was observed in both cases. Immunostaining for HLA-DR revealed a dense collection of cells within grafts from both cases. HLA-DR staining was rarely observed within the host including non-grafted regions of the striatum. A more detailed analysis of immune markers was performed in Case 2. Numerous pan macrophages, T-cells, and B-cells were observed within graft sites located in the postcommissural putamen. In contrast, staining for these immune cells was not observed within the ungrafted anterior putamen. These findings suggest that even in healthy appearing functional nigral implants, grafts are invaded by host immune cells that could compromise their long-term viability and function. Alternatively, immune cells are known to secrete trophic factors, which may ultimately favor graft survival and function. Further work is needed to understand the role of the immune system in fetal grafting.

Neural Transplantation for Huntington's Disease: Experimental Rationale and Recommendations for Clinical Trials

Huntington's disease (HD) is a neurodegenerative disorder affecting motor function, personality, and cognition. This paper reviews the experimental data that demonstrate the potential for transplantation of fetal striatum and trophic factor secreting cells to serve as innovative treatment strategies for HD. Transplantation strategies have been effective in replacing lost neurons or preventing the degeneration of neurons destined to die in both rodent and nonhuman primate models of HD. In this regard, a logical series of investigations has proven that grafts of fetal striatum survive, reinnervate the host, and restore function impaired following excitotoxic lesions of the striatum. Furthermore, transplants of cells genetically modified to secrete trophic factors such as nerve growth factor protect striatal neurons from degeneration due to excitotoxicity or mitochondrial dysfunction. Given the disabling and progressive nature of HD, coupled with the absence of any meaningful medical therapy, it is reasonable to consider clinical trials of neural transplantation for this disease. Fetal striatal implants will most likely be the first transplant strategy attempted for HD. This paper describes the variable parameters we believe to be critical for consideration for the design of clinical trials using fetal striatal implants for the treatment of HD.

Post-mortem assessment of the short and long-term effects of the trophic factor neurturin in patients with α-synucleinopathies

Substantial interest persists for developing neurotrophic factors to treat neurodegenerative diseases. At the same time, significant progress has been made in implementing gene therapy as a means to provide long-term expression of bioactive neurotrophic factors to targeted sites in the brain. Nonetheless, to date, no double-blind clinical trial has achieved positive results on its primary endpoint despite robust benefits achieved in animal models. A major issue with advancing the field is the paucity of information regarding the expression and effects of neurotrophic factors in human neurodegenerative brain, relative to the well-characterized responses in animal models. To help fill this information void, we examined post-mortem brain tissue from four patients with nigrostriatal degeneration who had participated in clinical trials testing gene delivery of neurturin to the putamen of patients. Each had died of unrelated causes ranging from 1.5-to-3-months (2 Parkinson's disease patients), to 4+-years (1 Parkinson's disease and 1 multiple-system atrophy-parkinsonian type patient) following gene therapy. Quantitative and immunohistochemical evaluation of neurturin, alpha-synuclein, tyrosine hydroxylase (TH) and an oligodendroglia marker (Olig 2) were performed in each brain. Comparable volumes-of-expression of neurturin were seen in the putamen in all cases (~15-22%; mean=18.5%). TH-signal in the putamen was extremely sparse in the shorter-term cases. A 6-fold increase was seen in longer-term cases, but was far less than achieved in animal models of nigrostriatal degeneration with similar or even far less NRTN exposure. Less than 1% of substantia nigra (SN) neurons stained for neurturin in the shorter-term cases. A 15-fold increase was seen in the longer-term cases, but neurturin was still only detected in ~5% of nigral cells. These data provide unique insight into the functional status of advanced, chronic nigrostriatal degeneration in human brain and the response of these neurons to neurotrophic factor stimulation. They demonstrate mild but persistent expression of gene-mediated neurturin over 4-years, with an apparent, time-related amplification of its transport and biological effects, albeit quite weak, and provide unique information to help plan and design future trials.

Attenuation of microglial RANTES by NEMO-binding domain peptide inhibits the infiltration of CD8(+) T cells in the nigra of hemiparkinsonian monkey

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). Despite intense investigations, little is known about its pathological mediators. Here, we report the marked upregulation of RANTES (regulated on activation, normal T cell expressed and secreted) and eotaxin, chemokines that are involved in T cell trafficking, in the serum of hemiparkinsonian monkeys. Interestingly, 1-methyl-4-phenylpyridinium (MPP(+)), a Parkinsonian toxin, increased the expression of RANTES and eotaxin in mouse microglial cells. The presence of NF-κB binding sites in promoters of RANTES and eotaxin and down-regulation of these genes by NEMO-binding domain (NBD) peptide, selective inhibitor of induced NF-κB activation, in MPP(+)-stimulated microglial cells suggest that the activation of NF-κB plays an important role in the upregulation of these two chemokines. Consistently, serum enzyme-linked immuno assay (ELISA) and nigral immunohistochemistry further confirmed that these chemokines were strongly upregulated in MPTP-induced hemiparkinsonian monkeys and that treatment with NBD peptides effectively inhibited the level of these chemokines. Furthermore, the microglial upregulation of RANTES in the nigra of hemiparkinsonian monkeys could be involved in the altered adaptive immune response in the brain as we observed greater infiltration of CD8(+) T cells around the perivascular niche and deep brain parenchyma of hemiparkinsonian monkeys as compared to control. The treatment of hemiparkinsonian monkeys with NBD peptides decreased the microglial expression of RANTES and attenuated the infiltration of CD8(+) T cells in nigra. These results indicate the possible involvement of chemokine-dependent adaptive immune response in Parkinsonism.

NGF receptor (p75)-immunoreactivity within hypoglossal motor neurons following axotomy in monkeys

The expression of the p75 nerve growth factor receptor (NGFR) was examined in Rhesus and Cebus monkeys following complete unilateral transections of the hypoglossal nerve. In unoperated and sham-lesioned monkeys, NGF receptor-immunoreactivity was always undetectable within hypoglossal motor neurons. In contrast, monkeys receiving unilateral transections of the hypoglossal nerve displayed numerous NGFR-immunoreactive neurons within ipsilateral hypoglossal motor neurons 1 week post-lesion. The peak expression of NGFR-immunoreactive hypoglossal neurons was seen 4 weeks following the lesion and although fewer, these neurons were still observed in large numbers 10 weeks post-lesion. By 16 weeks post-lesion only a few NGFR-immunoreactive motor neurons were observed. A small number of NGF receptor-immunoreactive neurons were also seen within the contralateral hypoglossal nucleus at post-lesion weeks 4 and 10. These data demonstrate that adult hypoglossal motor neurons express detectable levels of p75 nerve growth factor receptor following hypoglossal nerve transection in monkeys in a manner similar to that previously reported in non-primate species. The synthesis of p75 NGF receptors in these neurons may represent a regeneration-mediated re-expression of NGF receptors which only normally occurs during development.

Prenatal exposure to MDMA alters noradrenergic neurodevelopment in the rat

3,4-methylenedioxymethamphetamine (MDMA; ecstasy) binds with high affinity to the norepinephrine transporter (NET), making the noradrenergic system a potential target during fetal exposure. Recent data indicate that adult rats that had been prenatally exposed to MDMA display persistent deficits in working memory and attention; behaviors consistent with abnormal noradrenergic signaling in the forebrain. The present study was designed to investigate whether prenatal exposure to MDMA from embryonic days 14-20 affects the structure and/or function of the noradrenergic system of the rat on postnatal day 21. Offspring that were prenatally exposed to MDMA exhibited an increase in noradrenergic fiber density in the prelimbic region of the prefrontal cortex and the CA1 region of the hippocampus that was not accompanied by an increase in the number of noradrenergic neurons in the locus coeruleus. Direct tissue autoradiography using tritiated nisoxetine demonstrated that while NET binding was not altered in the prelimbic cortex, the dentate gyrus, or the locus coeruleus, it was increased in the CA1, CA2, and CA3 regions of the hippocampus. Basal levels of norepinephrine were increased in the prefrontal cortex and the nucleus accumbens of MDMA-exposed rats, as compared to saline-treated controls. These findings indicate that prenatal exposure to MDMA results in structural changes in the noradrenergic system as well as functional alterations in NE neurotransmission in structures that are critical in attentional processing.

Response of aged parkinsonian monkeys to in vivo gene transfer of GDNF

This study assessed the potential for functional and anatomical recovery of the diseased aged primate nigrostriatal system, in response to trophic factor gene transfer. Aged rhesus monkeys received a single intracarotid infusion of MPTP, followed one week later by MRI-guided stereotaxic intrastriatal and intranigral injections of lentiviral vectors encoding for glial derived neurotrophic factor (lenti-GDNF) or beta-galactosidase (lenti-LacZ). Functional analysis revealed that the lenti-GDNF, but not lenti-LacZ treated monkeys displayed behavioral improvements that were associated with increased fluorodopa uptake in the striatum ipsilateral to lenti-GDNF treatment. GDNF ELISA of striatal brain samples confirmed increased GDNF expression in lenti-GDNF treated aged animals that correlated with functional improvements and preserved nigrostriatal dopaminergic markers. Our results indicate that the aged primate brain challenged by MPTP administration has the potential to respond to trophic factor delivery and that the degree of neuroprotection depends on GDNF levels.

Age-related changes in dopamine transporters and accumulation of 3-nitrotyrosine in rhesus monkey midbrain dopamine neurons: relevance in selective neuronal vulnerability to degeneration

Aging is the strongest risk factor for developing Parkinson's disease (PD). There is a preferential loss of dopamine (DA) neurons in the ventral tier of the substantia nigra (vtSN) compared to the dorsal tier and ventral tegmental area (VTA) in PD. Examining age-related and region-specific differences in DA neurons represents a means of identifying factors potentially involved in vulnerability or resistance to degeneration. Nitrative stress is among the factors potentially underlying DA neuron degeneration. We studied the relationship between 3-nitrotyrosine (3NT; a marker of nitrative damage) and DA transporters [DA transporter (DAT) and vesicular monoamine transporter-2 (VMAT)] during aging in DA subregions of rhesus monkeys. The percentage of DA neurons containing 3NT increased significantly only in the vtSN with advancing age, and the vtSN had a greater percentage of 3NT-positive neurons when compared to the VTA. The relationship between 3NT and DA transporters was determined by measuring fluorescence intensity of 3NT, DAT and VMAT staining. 3NT intensity increased with advancing age in the vtSN. Increased DAT, VMAT and DAT/VMAT ratios were associated with increased 3NT in individual DA neurons. These results suggest nitrative damage accumulates in midbrain DA neurons with advancing age, an effect exacerbated in the vulnerable vtSN. The capacity of a DA neuron to accumulate more cytosolic DA, as inferred from DA transporter expression, is related to accumulation of nitrative damage. These findings are consistent with a role for aging-related accrual of nitrative damage in the selective vulnerability of vtSN neurons to degeneration in PD.

A confocal microscopic analysis of galaninergic hyperinnervation of cholinergic basal forebrain neurons in Alzheimer's disease

The galanin (GAL) containing peptide fiber system innervates the basal forebrain and has been shown to hyperinnervate remaining cholinergic neurons in Alzheimer's disease (AD). GAL modulates the release of acetylcholine and, therefore, may depress this neurotransmitter in surviving cholinergic basal forebrain (CBF) neurons in AD. The aim of this study was to identify putative synaptic contacts between GAL immunoreactive processes and CBF neurons and evaluate whether these processes hypertrophy in AD patients. We observed by confocal laser microscopy a hyperinnervation of GAL-containing fibers in both AD and Parkinson's disease patients with concurrent AD (PD/AD). Galaninergic fibers were often seen in direct apposition to remaining CBF neurons and enwrapped cholinergic cell soma and dendrites. Our results demonstrate that GAL-containing fibers are in direct apposition to CBF neurons in normal-aged humans and that this phenotype is enhanced in AD and PD/AD, suggesting that direct synaptic contacts occur between GAL-containing fibers and CBF neurons. Because GAL can modulate acetylcholine release from cholinergic neurons, hyperinnervation of GAL fibers in AD and PD/AD patients may further decrease release of acetylcholine from remaining CBF neurons. We propose that therapies based solely on acetylcholinesterase inhibitors may be insufficient to effectively increase cortical levels of acetylcholine.

Basal ganglia lesions after MPTP administration in rhesus monkeys

In monkeys, intracarotid infusion of a single low dose of MPTP reliably induces a hemiparkinsonian syndrome that is stable over time. This model has been widely used to assess novel anti-parkinsonian therapies. Here, we report the exceptional finding of severe necrotic lesions that were observed in the basal ganglia (but not in the substantia nigra) of monkeys that received a single intracarotid injection of MPTP followed by gene therapy treatments. Although extensive unilateral dopaminergic nigrostriatal loss was found in all the animals, partial behavioral recovery was observed in the subjects that presented pallidal necrotic lesions. This report discusses possible causes and effects of the necrotic lesions and their locations and the value of the intracarotid MPTP model. Testing novel therapies in monkey models has become an essential step before clinical trials. These results indicate that evaluation of any treatment should consider possible confounding factors that may affect the results.

Estrogen receptor alpha containing neurons in the monkey forebrain: lack of association with calcium binding proteins and choline acetyltransferase

The present study used single and dual immunohistochemistry to determine the topography and chemical phenotype of ERalpha containing neurons within the monkey forebrain utilizing antibodies directed against the full-length human ERalpha (NCL-ER-6F11), calcium-binding proteins calbindin-D(28k), and parvalbumin as well as choline acetyltransferase (ChAT). Our findings demonstrate for the first time ERalpha immunoreactive (-ir) cells in the monkey cerebral cortex (layers I-II) and in the claustrum. In addition, ERalpha-ir cells were seen in the septum, basal forebrain, amygdala and hypothalamus. Double-labeled cells for ERalpha and calbindin-D(28k) were seen only in the ventrolateral part of the ventromedial hypothalamic nucleus. In contrast, the co-localization of ERalpha and parvalbumin or ChAT was not seen in any of the areas of the monkey forebrain examined. These observations suggest that estrogens, at least in part, via ERalpha regulate calbindin-D(28k) hypothalamic but not parvalbumin or ChAT containing neurons in select monkey forebrain regions.

Down-regulation of trkA mRNA within nucleus basalis neurons in individuals with mild cognitive impairment and Alzheimer's disease

Recent studies indicate that trkA expression is reduced in end-stage Alzheimer's disease (AD). However, understanding the neuropathologic correlates of early cognitive decline, as well as the changes that underlie the transition from nondemented mild cognitive impairment (MCI) to AD, are more critical neurobiological challenges. In these regards, the present study examined the expression of trkA mRNA in individuals diagnosed with MCI and AD from a cohort of people enrolled in a Religious Orders Study. Individuals with MCI and AD displayed significant reductions in trkA mRNA relative to aged-matched controls, indicating that alterations in trkA gene expression occur early in the disease process. The magnitude of change was similar in MCI and AD cases, suggesting that further loss of trkA mRNA is not necessarily associated with the transition of individuals from nondemented MCI to AD. The loss of trkA mRNA was not associated with education, apolipoprotein E allele status, gender, Braak score, global cognitive score or Mini-Mental Status Examination. In contrast, the loss of trkA mRNA in MCI and AD was significantly correlated with function on a variety of episodic memory tests.

Early degenerative changes in transgenic mice expressing mutant huntingtin involve dendritic abnormalities but no impairment of mitochondrial energy production

Mitochondrial defects, which occur in the brain of late-stage Huntington's disease (HD) patients, have been proposed to underlie the selective neuronal loss in the disease. To shed light on the possible role of mitochondrial energy impairment in the early phases of HD pathophysiology, we carried out Golgi impregnation and quantitative histochemical/biochemical studies in HD full-length cDNA transgenic mice that were symptomatic but had not developed to a stage in which neuronal loss could be documented. Golgi staining showed morphologic abnormalities that included a significant decrease in the number of dendritic spines and a thickening of proximal dendrites in striatal and cortical neurons. In contrast, measurements of mitochondrial electron transport Complexes I-IV did not reveal changes in the striatum and cerebral cortex in these mice. Examination of the neostriatum and cerebral cortex in human presymptomatic and pathological Grade 1 HD cases also showed no change in the activity of mitochondrial Complexes I-IV. These data suggest that dendritic alterations precede irreversible cell loss in HD, and that mitochondrial energy impairment is a consequence, rather than a cause, of early neuropathological changes.

Systemic administration of the immunophilin ligand GPI 1046 in MPTP-treated monkeys

Systemic administration of immunophilin ligands provides trophic influences to dopaminergic neurons in rodent models of Parkinson's disease (PD) resulting in the initiation of clinical trials in patients with Parkinson's disease. We believe that prior to clinical trials, novel therapeutic strategies should show safety and efficacy in nonhuman models of PD. The present study assessed whether oral administration of the immunophilin 3-(3-pyridyl)-1-propyl (2S)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrollidinecarboxylate (GPI 1046) could prevent the structural and functional consequences of n-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in nonhuman primates. Twenty-five rhesus monkeys received daily oral administration of vehicle (n = 5) or one of four doses of GPI 1046 (0.3 mg/kg, n = 5; 1.0 mg/kg, n = 5; 3.0 mg/kg, n = 5; 10.0 mg/kg, n = 5). Two weeks after starting the drug treatment, all monkeys received a unilateral intracarotid injection of MPTP-HCl (3 mg). Daily drug administration continue for 6 weeks postlesion after which time the monkeys were sacrificed. Monkeys were assessed for performance on a hand reach task, general activity, and clinical dysfunction based on a clinical rating scale. All groups of monkeys displayed similar deficits on each behavioral measure as well as similar losses of tyrosine hydroxylase (TH)-immunoreactive (ir) nigral neurons, TH-mRNA, and TH-ir striatal optical density indicating that in general treatment failed to have neuroprotective effects.

Loss and atrophy of layer II entorhinal cortex neurons in elderly people with mild cognitive impairment

Layer II of the entorhinal cortex contains the cells of origin for the perforant path, plays a critical role in memory processing, and consistently degenerates in end-stage Alzheimer's disease. The extent to which neuron loss in layer II of entorhinal cortex is related to mild cognitive impairment without dementia has not been extensively investigated. We analyzed 29 participants who came to autopsy from our ongoing longitudinal study of aging and dementia composed of religious clergy (Religious Orders Study). All individuals underwent detailed clinical evaluation within 12 months of death and were categorized as having no cognitive impairment (n = 8), mild cognitive impairment (n = 10), or mild or moderate Alzheimer's disease (n = 11). Sections through the entorhinal cortex were immunoreacted with an antibody directed against a neuron-specific nuclear protein (NeuN). Stereological counts of NeuN-immunoreactive stellate cells, their volume, and the volume of layer II entorhinal cortex were estimated. Cases exhibiting no cognitive impairment averaged 639,625 +/- 184,600 layer II stellate neurons in the right entorhinal cortex. Individuals with mild cognitive impairment (63.5%; p < 0.0003) and mild or moderate Alzheimer's disease (46.06%; p < 0.0017) displayed significant losses of layer II entorhinal cortex neurons relative to those with no cognitive impairment but not relative to each other (p > 0.33). There was also significant atrophy of layer II entorhinal cortex neurons in individuals with mild cognitive impairment (24.1%) and Alzheimer's disease (25.1%). The volume of layer II was also reduced in individuals with mild cognitive impairment (26.5%), with a further reduction in those with Alzheimer's disease (46.4%). The loss and atrophy of layer II entorhinal cortex neurons significantly correlated with performance on clinical tests of declarative memory. Atrophy of layer II entorhinal cortex and the neurons within this layer significantly correlated with performance on the Mini Mental Status Examination. These data indicate that atrophy and loss of layer II entorhinal cortex neurons occur in elderly subjects with mild cognitive impairment prior to the onset of dementia and suggests that these changes are not exacerbated in early Alzheimer's disease.

Transplanted fetal striatum in Huntington's disease: phenotypic development and lack of pathology

Neural and stem cell transplantation is emerging as a potential treatment for neurodegenerative diseases. Transplantation of specific committed neuroblasts (fetal neurons) to the adult brain provides such scientific exploration of these new potential therapies. Huntington's disease (HD) is a fatal, incurable autosomal dominant (CAG repeat expansion of huntingtin protein) neurodegenerative disorder with primary neuronal pathology within the caudate-putamen (striatum). In a clinical trial of human fetal striatal tissue transplantation, one patient died 18 months after transplantation from cardiovascular disease, and postmortem histological analysis demonstrated surviving transplanted cells with typical morphology of the developing striatum. Selective markers of both striatal projection and interneurons such as dopamine and c-AMP-related phosphoprotein, calretinin, acetylcholinesterase, choline acetyltransferase, tyrosine hydroxylase, calbindin, enkephalin, and substance P showed positive transplant regions clearly innervated by host tyrosine hydroxylase fibers. There was no histological evidence of immune rejection including microglia and macrophages. Notably, neuronal protein aggregates of mutated huntingtin, which is typical HD neuropathology, were not found within the transplanted fetal tissue. Thus, although there is a genetically predetermined process causing neuronal death within the HD striatum, implanted fetal neural cells lacking the mutant HD gene may be able to replace damaged host neurons and reconstitute damaged neuronal connections. This study demonstrates that grafts derived from human fetal striatal tissue can survive, develop, and are unaffected by the disease process, at least for 18 months, after transplantation into a patient with HD.

Ontogeny of the dopamine D2 receptor mRNA expressing cells in the human hippocampal formation and temporal neocortex

The study details the cellular expression of the dopamine D2 receptor mRNA in the human temporal lobe during prenatal development. At 13 embryonic weeks (E13) D2 mRNA was widely expressed in the temporal lobe. At this time point in the dentate gyrus D2 mRNA positive cells first appeared at the outer border of the granular layer and their number increased with development. The CA1 exhibited the highest level of D2 mRNA expression. By E19-25 the hippocampal formation underwent rapid morphological maturation. D2 mRNA expression became more uniform and dense in the ammonic subfield. At all ages the subiculum appeared more mature morphologically but less intensely stained for D2 mRNA than the ammonic fields. In the entorhinal cortex D2 mRNA expression was most conspicuous in the future layer II at all ages. In the temporal neocortex D2 mRNA-positive cells were detected in the subplate and cortical plate. Differentiation of the cortical plate was accompanied by concentration of D2 mRNA-positive cells in layer V. The most conspicuous cells expressing D2 mRNA were found in the marginal zone of all regions and resembled Cajal-Retzius cells in morphology and location. Density of putative Cajal-Retzius cells expressing D2 mRNA decreased with development. They all but disappeared from the hippocampal areas by mid gestation, but in the temporal neocortex occasional cells were seen even at term. Early and widespread but region and cell type specific expression of D2 receptor mRNA suggests an important role of this DA receptor subtype in prenatal development of the human temporal lobe.

Loss of nucleus basalis neurons containing trkA immunoreactivity in individuals with mild cognitive impairment and early Alzheimer's disease

Recent studies indicate that there is a marked reduction in trkA-containing nucleus basalis neurons in end-stage Alzheimer's disease (AD). We used unbiased stereological counting procedures to determine whether these changes extend to individuals with mild cognitive impairment (MCI) without dementia from a cohort of people enrolled in the Religious Orders Study. Thirty people (average age 84.7 years) came to autopsy. All individuals were cognitively tested within 12 months of death (average MMSE 24.2). Clinically, 9 had no cognitive impairment (NCI), 12 were categorized with MCI, and 9 had probable AD The average number of trkA-immunoreactive neurons in persons with NCI was 196, 632 +/- 12,093 (n = 9), for those with MCI it was 106,110 +/- 14,565, and for those with AD it was 86,978 +/- 12,141. Multiple comparisons showed that both those with MCI and those with AD had significant loss in the number of trkA-containing neurons compared to those with NCI (46% decrease for MCI, 56% for AD). An analysis of variance revealed that the total number of neurons containing trkA immunoreactivity was related to diagnostic classification (P < 0.001), with a significant reduction in AD and MCI compared to NCI but without a significant difference between MCI and AD. Cell density was similarly related to diagnostic classification (P < 0.001). There was a significant correlation with the Boston Naming Test and with a global score measure of cognitive function. The number of trkA-immunoreactive neurons was not correlated with MMSE, age at death, education, apolipoprotein E allele status, gender, or Braak score. These data indicate that alterations in the number of nucleus basalis neurons containing trkA immunoreactivity occurs early and are not accelerated from the transition from MCI to mild AD.

B2 bradykinin receptor immunoreactivity in rat brain

Bradykinin has long been known to exist in the central nervous system and has been hypothesized to mediate specific functions. Despite an increasing understanding of the functions of bradykinin, little is known about the cell types expressing the bradykinin receptor within the brain. The present investigation employed a monoclonal antibody directed against the 15-amino-acid portion of the C-terminal of the human bradykinin B2 receptor to establish the cellular distribution of bradykinin B2 receptor immunoreactivity in the rat brain. Bradykinin B2 receptor immunoreactivity was ubiquitously and selectively observed in neurons, including those within the olfactory bulb, cerebral cortex, hippocampus, basal forebrain, basal ganglia, thalamus, hypothalamus, cerebellum, and brainstem nuclei. Bradykinin B2 receptor immunoreactivity was also present in the circumventricular organs including choroid plexus, subfornical organ, median eminence, and area postrema. Double-labeling experiments colocalizing the bradykinin B2 receptor with the neuronal marker NeuN or the astrocytic marker glial fibrillary acidic protein revealed that virtually 100% of the bradykinin B2 receptor-immunoreactive positive cells were neurons. The widespread distribution of bradykinin B2 receptor immunoreactivity in neuronal compartments suggests a greater than previously appreciated role for this peptide in neuronal function.

Age-related decreases in GTP-cyclohydrolase-I immunoreactive neurons in the monkey and human substantia nigra

Guanosine triphosphate cyclohydrolase I (GTPCHI) is a critical enzyme in catecholamine function and is rate limiting for the synthesis of the catecholamine co-factor tetrahydrobiopterin. The present study assessed the distribution of GTPCHI immunoreactivity (-ir) within the monkey and human ventral midbrain and determined whether its expression is altered as a function of age. Light and confocal microscopic analyses revealed that young monkeys and humans displayed GTPCHI-ir within melanin-containing and tyrosine-hydroxylase-ir neurons in primate substantia nigra. Stereological counts revealed that there was a 67.4% reduction in GTPCHI-ir neuronal number, a 63.5% reduction in GTPCHI-ir neuronal density, and a 37.6% reduction in neuronal volume in aged monkeys relative to young cohorts. Similar age-related changes were seen in humans, in whom there were significant reductions in the number of GTPCHI-ir nigral neurons in middle age (58.4%) and aged (81.5%) cases relative to young cohorts. The density of GTPCHI-ir neurons within the nigra was similarly reduced in middle-aged (63.0%) and aged (81.8%) cases. In contrast to monkeys, aged humans did not display shrinkage in the volume of GTPCHI-ir nigral neurons. The presence of numerous melanin-positive, but GTPCHI-ir immunonegative, neurons in the aged monkey and human nigra indicates that these decreases represent an age-related phenotypic downregulation of this enzyme and not a loss of neurons per se. These data indicate that there is a dramatic decrease in GTPCHI-ir in nonhuman primates and humans as a function of age and that loss of this enzyme may be partly responsible for the age-related decrease in dopaminergic tone within nigrostriatal systems.

Neurodegeneration prevented by lentiviral vector delivery of GDNF in primate models of Parkinson's disease

Lentiviral delivery of glial cell line-derived neurotrophic factor (lenti-GDNF) was tested for its trophic effects upon degenerating nigrostriatal neurons in nonhuman primate models of Parkinson's disease (PD). We injected lenti-GDNF into the striatum and substantia nigra of nonlesioned aged rhesus monkeys or young adult rhesus monkeys treated 1 week prior with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive GDNF expression with anterograde and retrograde transport was seen in all animals. In aged monkeys, lenti-GDNF augmented dopaminergic function. In MPTP-treated monkeys, lenti-GDNF reversed functional deficits and completely prevented nigrostriatal degeneration. Additionally, lenti-GDNF injections to intact rhesus monkeys revealed long-term gene expression (8 months). In MPTP-treated monkeys, lenti-GDNF treatment reversed motor deficits in a hand-reach task. These data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients.

Cyclosporin A protects striatal neurons in vitro and in vivo from 3-nitropropionic acid toxicity

The neuroprotective properties of cyclosporin A (CsA) are mediated by its ability to prevent mitochondrial permeability transition during exposure to high levels of calcium or oxidative stress. By using the mitochondrial toxin 3-nitropropionic acid (3NP), the present study assessed whether CsA could protect striatal neurons in vitro and in vivo. In vitro, 3NP produced a 20-30% reduction of striatal glutamic acid decarboxylase-immunoreactive (GAD-ir) neurons. A single treatment with CsA protected GAD-ir neurons from 3NP toxicity at lower (0.2 or 1.0 microM), but not at higher (5.0 microM) doses. Similar findings were seen when the cultures were treated twice with cyclosporin. In vivo experiments used the Lewis rat model of Huntington's disease (HD) in which a low 3NP dose was delivered subcutaneously through an osmotic minipump. Rats received unilateral or bilateral intrastriatal saline injections to disrupt the blood-brain barrier (BBB) and facilitate CsA reaching vulnerable neurons. In the first experiment, CsA treated 3NP-lesioned rats displayed significantly more dopamine-and adenosine-3;, 5;-monophosphate-regulated phosphoprotein (DARPP32-ir) neurons ipsilateral to BBB disruption compared to the contralateral intact striatum, indicating that disruption of the BBB maybe necessary for CsA's neuroprotective effects. In the second experiment, stereological counts of DARPP32-ir neurons revealed that CsA protected striatal neurons in a dose-dependent manner following bilateral disruption of the striatal BBB. Rats treated with the higher (15 or 20 mg/kg) but not lower (5 mg/kg) doses of CsA displayed greater numbers of DARRP32-ir striatal neurons relative to vehicle-treated 3NP-lesioned rats. Thus, under conditions in which CsA can gain access to striatal neurons, significant protection from 3NP toxicity is observed. Therefore, CsA or more lipophilic analogues of this compound, may be of potential therapeutic benefit by protecting vulnerable neurons from the primary pathological event observed in HD.

Delayed onset of progressive dystonia following subacute 3-nitropropionic acid treatment in Cebus apella monkeys

Delayed abnormal movements can be observed in patients with acute neurologic insult after a prolonged period of apparent neurologic stability. To reproduce such a secondary neurologic manifestation in primates, the present experiment investigated whether systemic administration of subacute 3-nitropropionic acid (3NP), a mitochondrial toxin, could induce abnormal movements that were delayed and progressive over time. Four Cebus apella monkeys received systemic 3NP injections until acute neurologic signs manifested. The monkeys were regularly video-recorded and rated for abnormal movements for up to 15 weeks after the cessation of 3NP treatment. Five to 6 weeks after the 3NP treatment, monkeys displayed a significant increase in dyskinesias compared with pretreatment conditions. Over time the chorea attenuated, whereas the dystonic movements increased in intensity and severity which was characterized by a delayed decrease of peak tangential velocity. The intensity of abnormal movements and extent of affected body regions observed in each monkey were consistent with the size of basal ganglia hypersignal as documented by T2 sequence on magnetic resonance imaging. Thus, more severe motor impairments were associated with large magnetic resonance image abnormalities. This novel primate model may be particularly useful for studying the structural changes underlying delayed and progressive manifestations of abnormal movements with the ultimate goal of facilitating the evaluation of novel therapeutic strategies.

Reduction in TrkA-immunoreactive neurons is not associated with an overexpression of galaninergic fibers within the nucleus basalis in Down's syndrome

Down's syndrome (DS) individuals develop neuropathological features similar to Alzheimer's disease (AD), including degeneration of cholinergic basal forebrain (CBF) neurons. In AD a reduction in CBF/trkA-containing neurons has been suggested to trigger a hyperexpression of galaninergic fibers within the nucleus basalis subfield of the basal forebrain. The present study examined the interrelationship between reductions in CBF/trkA-containing neurons and the overexpression of galaninergic fibers within the nucleus basalis in DS. Within the nucleus basalis stereologic evaluation revealed a 46% reduction in the number of trkA-immunopositive neurons, whereas optical density measurements displayed a nonsignificant 18% reduction in neuronal trkA immunoreactivity in DS as compared with age-matched controls. Western blot analysis also showed a significant reduction in cortical trkA protein levels in DS. A semiquantitative examination of galaninergic fibers in the nucleus basalis revealed only a modest hypertrophy of galaninergic fibers within the nucleus basalis in DS. The present findings indicate a significant reduction in trkA within the nucleus basalis and cortex with only a moderate hypertrophy of galaninergic fibers in DS. These observations suggest that DS may not be an exact genetic model for investigation of changes in the AD basal forebrain.

Evidence that Cereport's ability to increase permeability of rat gliomas is dependent upon extent of tumor growth: implications for treating newly emerging tumor colonies

Cereport (RMP-7) enhances delivery of chemotherapeutics into brain tumors by increasing the permeability of the glioma vasculature (i.e. , the blood-brain tumor barrier; BBTB). Its effect on brain tumors has consistently been more robust than that on normal brain. The present experiments tested the hypothesis that the ability of Cereport to increase the permeability of infiltrating glioma colonies increases as the glioma colonies develop, in situ. In an initial preliminary experiment, the significant and selective effects of Cereport in tumor tissue and brain surrounding tumor were verified using [(14)C]carboplatin as a marker, 8 days after implantation of 50,000 RG2 cells. A second preliminary experiment established that the number of tumor cells initially seeded influences the growth rate of the tumor mass. Tumors seeded with 50,000 cells were larger than those seeded with 25,000 cells 3, 5, and 8 days after implantation. Next, the hypothesis that the extent of tumor growth increases Cereport's effects on the BBTB was tested by measuring the concentration of radiolabeled carboplatin in the tumor when 50,000 cells were implanted 3, 8, or 13 days prior to the experiment. While a reliable, approximately twofold increase in carboplatin concentration was seen in the 8- and 13-day-old tumors, no significant effect of Cereport was observed in the tumors that developed only 3 days, in situ. Finally, another test of the hypothesis was made by comparing Cereport's effects on 8-day-old tumors initially seeded with either 50,000 or 25,000 cells (the latter producing a smaller, more slowly developing, tumor mass). Again, significantly higher carboplatin concentrations were seen with Cereport in the 50,000 cell tumors (greater than two-fold increase), compared to the smaller, more slowly developing, 25,000 cell tumors (<30% increase). The tumor and its vasculature were characterized in additional rats implanted with RG2 cells using CD-31, laminin, and bradykinin B(2) receptor immunocytochemistry. Intense B(2) receptor staining was observed on cells within the parenchyma of normal brain and tumor but not on the vasculature of tumor or brain. An extensive network of CD-31 and laminin staining was seen within and around the tumors in all groups, indicating relatively rapid and robust changes in vascularity in response to the gliomas. However, no consistent difference in vascularity between groups was observed to account for the uptake differences seen with Cereport. Collectively, these data offer initial preclinical empirical support for the hypothesis that Cereport's effects on tumor permeability increase as the tumor grows, which we further hypothesize is likely related to features of vascular development within the tumor independent of numbers or general morphology of vessels. If a similar phenomenon is shown to occur with infiltrating colonies from spontaneously forming gliomas in humans or from newly emerging metastases in brain, these data could impact the design and conduct of future trials using approaches intended to enhance delivery of chemotherapeutics through increased permeability of the tumor vascular barrier.

Estrogen receptor immunoreactivity within subregions of the rat forebrain: neuronal distribution and association with perikarya containing choline acetyltransferase

Administration of the neuroactive steroid hormone estrogen has been shown to effect cholinergic basal forebrain neuronal function. Antibodies directed against the estrogen receptor alpha (ERalpha) revealed dark (type 1) and light (type 2) nuclear positive neurons within the islands of Calleja, endopiriform nucleus, lateral septum, subfields of the cholinergic basal forebrain, bed nucleus of the stria terminalis, striohypothalamic region, medial preoptic region, periventricular, ventromedial, arcuate and tuberal mammillary nuclei of the hypothalamus, reuniens and anterior medial thalamic nuclei, amygdaloid complex, piriform cortex and subfornical organ. In contrast, only a few scattered ERalpha labeled neurons were found in cortex and hippocampus. ERalpha stained cell bodies were not seen in the striatum. Counts of ERalpha labeled neurons in intact female rats revealed significantly more type 2 neurons within the basal forebrain subfields. Quantitation of ERalpha immunoreactive neurons revealed a significant decrease in the relative number of type 1 neurons within the medial septum (MS), horizontal limb of the diagonal band (HDB) and substantia innominata/nucleus basalis (SI/NB) following ovariectomy. Quantitation following choline acetyltransferease (ChAT) immunohistochemistry revealed a significant decrease in the number of ChAT positive neurons within the MS, HDB and SI/NB, but not VDB following ovariectomy. Following ovx, the percentage of double labeled cholinergic basal forebrain neurons also declined significantly within the MS, VDB, HDB and SI/NB. These observations suggest that estrogen effects a subpopulation of cholinergic basal forebrain neurons and may provide insight into the biologic actions of this steroid in Alzheimer's disease.

Lentiviral gene transfer to the nonhuman primate brain

Lentiviral vectors infect quiescent cells and allow for the delivery of genes to discrete brain regions. The present study assessed whether stable lentiviral gene transduction can be achieved in the monkey nigrostriatal system. Three young adult Rhesus monkeys received injections of a lentiviral vector encoding for the marker gene beta galatosidase (beta Gal). On one side of the brain, each monkey received multiple lentivirus injections into the caudate and putamen. On the opposite side, each animal received a single injection aimed at the substantia nigra. The first two monkeys were sacrificed 1 month postinjection, while the third monkey was sacrificed 3 months postinjection. Robust incorporation of the beta Gal gene was seen in the striatum of all three monkeys. Stereological counts revealed that 930,218; 1,192,359; and 1,501,217 cells in the striatum were beta Gal positive in monkeys 1 (n = 2) and 3 (n = 1) months later, respectively. Only the third monkey had an injection placed directly into the substantia nigra and 187,308 beta Gal-positive cells were identified in this animal. The injections induced only minor perivascular cuffing and there was no apparent inflammatory response resulting from the lentivirus injections. Double label experiments revealed that between 80 and 87% of the beta Gal-positive cells were neurons. These data indicate that robust transduction of striatal and nigral cells can occur in the nonhuman primate brain for up to 3 months. Studies are now ongoing testing the ability of lentivirus encoding for dopaminergic trophic factors to augment the nigrostriatal system in nonhuman primate models of Parkinson's disease.

Cellular delivery of trophic factors for the treatment of Huntington's disease: is neuroprotection possible?

The elucidation of the genetic defect in patients with Huntington's disease (HD) has allowed for the detection of individuals at risk for HD prior to the onset of symptoms. Thus "neuroprotection strategies" aimed at preventing the neuropathological and behavioral sequelae of this disease might be powerful therapeutically since they could be introduced to healthy patients before the initiation of a massive degenerative cascade principally localized to the striatum. A variety of trophic factors potently protect vulnerable striatal neurons in animal models of HD. A number of experimental variables are critical in determining the success of trophic factors in animal models. In this regard, the method of trophic factor delivery may be crucial, as delivery via genetically modified cells often produces greater and more widespread effects on striatal neurons than infusions of that same factor. The mechanisms by which cellularly delivered trophic factors forestall degeneration and prevent behavioral deficits are complex and often appear to be unrelated to the trophic factor binding to its cognate receptor. In this regard, cells genetically modified to secrete nerve growth factor (NGF) or ciliary neurotrophic factor (CNTF) protect degenerating striatal neurons which do not express either NGF or CNTF receptors. This review will discuss some of the non-receptor-based events that might underlie these effects and present the hypothesis that cellular delivery of certain trophic factors using genetically modified cells may be ready for clinical testing in HD patients.

Clinicopathological findings following intraventricular glial-derived neurotrophic factor treatment in a patient with Parkinson's disease

As part of a safety and tolerability study, a 65-year-old man with Parkinson's disease (PD) received monthly intracerebroventricular injections of glial-derived neurotrophic factor (GDNF). His parkinsonism continued to worsen following intracerebroventricular GDNF treatment. Side effects included nausea, loss of appetite, tingling, L'hermitte's sign, intermittent hallucinations, depression, and inappropriate sexual conduct. There was no evidence of significant regeneration of nigrostriatal neurons or intraparenchymal diffusion of the intracerebroventricular GDNF to relevant brain regions. Alternative GDNF delivery systems should be explored.

Entorhinal cortex beta-amyloid load in individuals with mild cognitive impairment

The deposition of beta-amyloid within the entorhinal cortex (EC) may play a key role in the development of mild cognitive impairment (MCI) in the elderly. To examine the relationship of beta-amyloid deposition to MCI, EC tissue immunostained for this protein was quantitated from a cohort of aged Catholic religious clergy with a clinical diagnosis of MCI and compared to those with no cognitive impairment (NCI) and Alzheimer's disease (AD). beta-amyloid staining was seen in 12 of the 20 NCI, in 10 of 12 MCI, and in all 12 AD cases within the EC. beta-amyloid immunoreactivity displayed two patterns within the EC: (1) a crescent-shaped band within layers 3-4 or (2) bilaminar staining mainly within layers 2-3 and 5-6. Ten cases failed to display any detectable beta-amyloid imunoreactivity. Despite the heterogeneity of beta-amyloid loads within the clinical groups, decomposing an analysis of variance revealed a significant difference across groups in mean beta-amyloid load within the EC based upon a linear trend analysis. Multiple comparisons testing revealed that NCI individuals had a significantly lower mean beta-amyloid load (1.32) than AD individuals (4.55). The MCI individuals had a mean intermediate (2.60) load between NCI and AD, but not statistically distinguishable from the mean for either NCI or AD. Spearman rank correlation showed a trend for decreasing MMSE with increasing amyloid load that failed to reach statistical significance. Since many NCI cases displayed beta-amyloid loads equal to or greater than that seen in some MCI and some AD cases, it is mostly likely that deposition of this protein is not the sole pathogenic event underlying cognitive impairment in the elderly.

Dopamine transporter-immunoreactive neurons decrease with age in the human substantia nigra

Unbiased disector stereologic cell counting was applied to sections from the human substantia nigra that were immunostained by using a monoclonal antibody against the dopamine transporter (DAT). This antibody was found to penetrate the full thickness of the stained section. Quantification of the number of DAT immunostained neurons was performed in human cases stratified into three age groups, young (ages 0-49 years), middle aged (ages 50-69 years), and aged (ages 70-85 years). The number of DAT-immunoreactive nigral neurons was normalized for each case by constructing a ratio of the number of DAT-containing neurons to total number of neuromelanin-containing cells in each subject's sample. Three types of DAT nigral neurons were seen: type 1, intensely stained; type 2, lightly stained; and type 3, DAT-immunonegative neuromelanin-containing perikarya. By 50 years of age, the number of type 1 neurons decreased significantly (P < 0.0001), whereas the number of type 2 neurons increased with age (P < 0.0001). Type 3 neurons also increased with age (P < 0.01), although less robustly than type 2 neurons. Type 1 neurons decreased by 11.2% per decade, and the total number of nigral neurons (types 1-3) decreased by 6.7% per decade. Relative to the young group, there were 75% and 88% reductions in type 1 neurons in the middle-aged and aged groups, respectively. This contrasts with the 35% and 41% reductions in total number of neuromelanin-containing neurons seen in middle-aged and aged groups, respectively. The young group had significantly more type 1 neurons and fewer type 2 neurons compared with middle-aged and aged participants. Post-hoc analyses indicated that the young group had significantly fewer type 3 neurons compared with middle-aged and aged participants. These findings demonstrate an age-related reduction in the number of substantia nigra DAT-immunoreactive neurons. Therefore, insight into the mechanisms regulating the rate of DAT synthesis may aid in our understanding of the decline of DATs with aging and its functional significance.

Long-term evaluation of bilateral fetal nigral transplantation in Parkinson disease

BACKGROUND

Parkinson disease (PD) is associated with a progressive loss of nigrostriatal dopamine neurons. Medication therapy provides adequate control of symptoms for several years, but long-term treatment is complicated by progressive disability and the development of motor fluctuations and dyskinesias. In animal models of PD, fetal nigral transplants have been shown to survive grafting into the striatum, provide extensive striatal reinnervation, and improve motor function. In patients with PD, cell survival and clinical benefit have been observed following fetal nigral grafting, but results have been inconsistent.

OBJECTIVE

To evaluate the safety and efficacy of bilateral fetal nigral transplantation into the postcommissural putamen in patients with advanced PD complicated by motor fluctuations and dyskinesias.

PATIENTS AND METHODS

Six patients with advanced PD underwent bilateral fetal nigral transplantation. Each patient received solid grafts derived from donors aged 6 1/2 to 9 weeks after conception stereotactically implanted into the postcommissural putamen using 3 to 4 donors per side. Cyclosporine was administered for approximately 6 months to provide immune suppression. Clinical evaluations included the Unified Parkinson's Disease Rating Scale (UPDRS), Schwab-England Activities of Daily Living Scale, and timed tests of motor function conducted during both the "off' and "on" states at baseline and at 1, 3, 6, 9, 12, 18, and 24 months following transplantation. Percentage of time off and percentage of time on with and without dyskinesia were recorded at half-hour intervals using home diaries during the week prior to each evaluation. 18F-fluorodopa positron emission tomographic scans were performed at baseline, and at 6 months and 1 year following transplantation.

RESULTS

Patients have been followed up for a mean+/-SD of 20.5+/-5.5 months. Complications related to surgery were mild and transient. Activities of daily living, motor, and total (activities of daily living plus motor) UPDRS scores during the off state improved significantly (P<.05, Wilcoxon signed rank test) at final visit in comparison with baseline. Mean total UPDRS off score improved 32%, and each patient experienced at least a 19% improvement. Mean percentage of time on without dyskinesia during the waking day improved from 22% to 60% (P<.05). Mean putamenal fluorodopa uptake on positron emission tomography increased significantly at 6 and 12 months in comparison with baseline (P<.001, 2-tailed t test). This increase correlated with clinical improvement. Two patients died 18 months after transplantation from causes unrelated to the surgical procedure. In both cases, histopathological examination showed robust survival of tyrosine hydroxylase immunoreactive cells and abundant reinnervation of the postcommissural putamen.

CONCLUSIONS

Fetal nigral tissue can be transplanted into the postcommissural putamen bilaterally in patients with advanced PD safely and with little morbidity. In this open-label pilot study we observed consistent long-term clinical benefit and increased fluorodopa uptake on positron emission tomography. Clinical improvement appears to be related to the survival and function of transplanted fetal tissue.

Cortical ablation induces a spreading calcium-dependent, secondary pathogenesis which can be reduced by inhibiting calpain

Many forms of acute brain injury are associated with a secondary, glutamate- and calcium-dependent cascade which greatly exacerbates the final damage. The calcium-dependent protease, calpain, has been implicated as an important variable in this pathogenic process. The present studies tested (i) if similar secondary degeneration occurs following surgical ablation of a discrete area within rat visual cortex, (ii) if activation of calpain contributes to the secondary degeneration by spreading into areas adjacent to the ablation, and (iii) if blocking calpain's proteolytic effects reduces the secondary degeneration attendant to the lesion. Antibodies selective for a protein fragment specifically generated by calpain were used to map areas in which the protease had been activated. Labeling was present 5 min after surgery in a narrow zone surrounding the ablated region. The volume of the immunopositive staining increased twofold within 24 h and fivefold by 48 h, at which time it was equivalent in size to the original lesion. This staining pattern significantly decreased in size at 5 days postsurgery. Application of calpain inhibitors to the ablation site immediately after surgery reduced the spread of calpain activation by approximately 80%. Following cortical ablation, the volume of the lateral geniculate nucleus ipsilateral to the cortical ablation shrank by 46 +/- 3% in control rats but only by 31 +/- 5% in animals given the calpain inhibitors. These results establish that (i) a secondary degenerative cascade is unleashed following discrete cortical surgery which expands into brain areas clearly outside the initial perturbation site, (ii) the gradual expansion of calpain activation contributes to the underlying secondary pathology, and (iii) blocking calpain activity substantially reduces atrophy in areas anatomically connected, but physically distal to the damaged zone. The possible utility of topical applications of calpain inhibitors, or analogously acting drugs, in minimizing the secondary effects of brain surgery is discussed.