Overexpressing Cu/Zn superoxide dismutase enhances survival of transplanted neurons in a rat model of Parkinson's disease

Superoxide dismutase and neurological disorders

Superoxide dismutase (SOD) is a common antioxidant enzyme found majorly in living cells. The main physiological role of SOD is detoxification and maintain the redox balance, acts as a first line of defence against Reactive nitrogen species (RNS), Reactive oxygen species (ROS), and other such potentially hazardous molecules. SOD catalyses the conversion of superoxide anion free radicals (O 2 -.) into molecular oxygen (O 2) and hydrogen peroxide (H 2O 2) in the cells. Superoxide dismutases (SODs) are expressed in neurons and glial cells throughout the CNS both intracellularly and extracellularly. Endogenous oxidative stress (OS) linked with enlarged production of reactive oxygen metabolites (ROMs), inflammation, deregulation of redox balance, mitochondrial dysfunction and bioenergetic crisis are found to be prerequisite for neuronal loss in neurological diseases. Clinical and genetic studies indicate a direct correlation between mutations in SOD gene and neurodegenerative diseases, like Amyotrophic Lateral Sclerosis (ALS), Huntington's disease (HD), Parkinson's Disease (PD) and Alzheimer's Disease (AD). Therefore, inhibitors of OS are considered as an optimistic approach to prevent neuronal loss. SOD mimetics like Metalloporphyrin Mn (II)-cyclic polyamines, Nitroxides and Mn (III)- Salen complexes are designed and used as therapeutic extensively in the treatment of neurological disorders. SODs and SOD mimetics are promising future therapeutics in the field of various diseases with OS-mediated pathology.

Design of Monovalent Cerium-Based Metal Organic Frameworks as Bioinspired Superoxide Dismutase Mimics for Ionizing Radiation Protection

Superoxide dismutase (SOD) is one of the major antioxidants in vivo and is expected to play critical roles on the defense against reactive oxygen species (ROS)-mediated damages, such as ionizing radiation damages. Herein, inspired by the function and structure of natural SODs and cerium oxide nanozymes, two monovalent cerium-based metal organic frameworks (Ce-MOFs), Ce^IIIBTC and Ce^IVBTC, were designed for superoxide radical (O₂^•-) elimination and ionizing radiation protection. These two Ce-MOFs selectively scavenge O₂^•- and are excellent SOD mimics. Like natural SODs and cerium oxide nanozymes, the SOD-like catalytic mechanism of Ce-MOFs involves a cycle between Ce(IV) and Ce(III). Furthermore, by constructing monovalent Ce-MOFs, we found that high-valent Ce^IVBTC are more effective SOD-like nanozymes compared to Ce^IIIBTC. With smaller size, better monodispersity, and more effective SOD-like activity, Ce^IVBTC nanozymes were further applied for ionizing radiation protection. Both in vitro and in vivo results demonstrated that Ce^IVBTC nanozymes could efficiently scavenge ROS, prevent cells from γ-ray radiation-induced cell viability decrease and DNA damages, and improve the survival rate of irradiated mice by recovering the bone marrow DNA damage and alleviating oxidative stress of tissues. The protective effect and good biocompatibility of Ce^IVBTC nanozymes will enable the development of Ce-MOFs-based radioprotectants and facilitate treatment of other ROS-related diseases.

Effects of Brain Factor‑7® against motor deficit and oxidative stress in a mouse model of MPTP‑induced Parkinson's disease

Oxidative stress is strongly implicated in the pathogenesis of Parkinson's disease (PD) through degeneration of dopaminergic neurons. The present study was designed to investigate the underlying mechanisms and therapeutic potential of Brain Factor-7^® (BF-7^®), a natural compound in silkworm, in a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP (20 mg/kg) was intraperitoneally injected into mice to cause symptoms of PD. Mice were orally administered BF-7^® (a mixture of silk peptides) before and after MPTP treatment. Rotarod performance test was used to assess motor performance. Fluoro-Jade B staining for neurons undergoing degeneration and immunohistochemistry of tyrosine hydroxylase for dopaminergic neurons, 4-hydroxy-2-nonenal (4HNE) for lipid peroxidation, 8-hydroxy-2'-deoxyguanosine (8OHdG) for DNA damage and superoxide dismutase (SOD) 1 and SOD2 for antioxidative enzymes in the pars compacta of the substantia nigra were performed. Results showed that BF-7^® treatment significantly improved MPTP-induced motor deficit and protected MPTP-induced dopaminergic neurodegeneration. Furthermore, BF-7^® treatment significantly ameliorated MPTP-induced oxidative stress. Increased 4HNE and 8OHdG immunoreactivities induced by MPTP were significantly reduced by BF-7^®, whereas SOD1 and SOD2 immunoreactivities decreased by MPTP were significantly enhanced by BF-7^®. In conclusion, BF-7^® exerted protective and/or therapeutic effects in a mouse model of PD by decreasing effects of oxidative stress on dopaminergic neurons in the substantia nigra pars compacta.

A combined cell and gene therapy approach for homotopic reconstruction of midbrain dopamine pathways using human pluripotent stem cells

Midbrain dopamine (mDA) neurons can be replaced in patients with Parkinson's disease (PD) in order to provide long-term improvement in motor functions. The limited capacity for long-distance axonal growth in the adult brain means that cells are transplanted ectopically, into the striatal target. As a consequence, several mDA pathways are not re-instated, which may underlie the incomplete restoration of motor function in patients. Here, we show that viral delivery of GDNF to the striatum, in conjunction with homotopic transplantation of human pluripotent stem-cell-derived mDA neurons, recapitulates brain-wide mDA target innervation. The grafts provided re-instatement of striatal dopamine levels and correction of motor function and also connectivity with additional mDA target nuclei not well innervated by ectopic grafts. These results demonstrate the remarkable capacity for achieving functional and anatomically precise reconstruction of long-distance circuitry in the adult brain by matching appropriate growth-factor signaling to grafting of specific cell types.

Chloramphenicol Mitigates Oxidative Stress by Inhibiting Translation of Mitochondrial Complex I in Dopaminergic Neurons of Toxin-Induced Parkinson's Disease Model

Paraquat (PQ), an herbicide considered an environmental contributor to the development of Parkinson's disease (PD), induces dopaminergic neuronal loss through reactive oxygen species (ROS) production and oxidative stress by mitochondrial complex I. Most patients with PQ-induced PD are affected by chronic exposure and require a preventive strategy for modulation of disease progression. To identify drugs that are effective in preventing PD, we screened more than 1000 drugs that are currently used in clinics and in studies employing PQ-treated cells. Of these, chloramphenicol (CP) showed the most powerful inhibitory effect. Pretreatment with CP increased the viability of PQ-treated SN4741 dopaminergic neuronal cells and rat primary cultured dopaminergic neurons compared with control cells treated with PQ only. CP pretreatment also reduced PQ-induced ROS production, implying that mitochondrial complex I is a target of CP. This effect of CP reflected downregulation of the mitochondrial complex I subunit ND1 and diminished PQ recycling, a major mechanism of ROS production, and resulted in the prevention of cell loss. Notably, these effects of CP were not observed in rotenone-pretreated SN4741 cells and Rho-negative cells, in which mitochondrial function is defective. Consistent with these results, CP pretreatment of MPTP-treated PD model mice also ameliorated dopaminergic neuronal cell loss. Our findings indicate that the inhibition of mitochondrial complex I with CP protects dopaminergic neurons and may provide a strategy for preventing neurotoxin-induced PD.

Human wild-type superoxide dismutase 1 gene delivery to rat bone marrow stromal cells: its importance and potential future trends

Objective(s):

Human superoxide dismutase 1 (SOD1) is the cytosolic form of this enzyme it detoxifies superoxide anions and attenuates their toxicities and concomitant detrimental effects on the cells. It is believed that the amount of these enzymes present in the oxidative stress-induced diseases is crucial for preventing disease progression. Transfection of rat bone marrow stromal cells (BMSCs) by a constructed vector carrying the human wild-type SOD1 gene, a non-viral gene transfer method, was the main aim of this study.

Materials and Methods:

For this purpose, the rat BMSCs were transfected with the vector using Turbofect reagent and then stabilized. Western-blot and real-time PCR were also used for evaluation of SOD1 expression.

Results:

Data analysis from RT-PCR and Western-blot techniques revealed that the stable transfected cells could secrete human wild-type SOD1 in the supernatant. Also, the total activity of SOD1 was about 0.5±0.09 U/ml and 0.005±0.002 U/ml in the supernatants of the transfected and not-transfected of rat BMSCs, respectively.

Conclusion:

This study showed that expansion of the stable transfected rat BMSCs by a constructed vector carrying the human wild-type SOD1 gene is capable of secreting the active SOD1 enzyme under ex-vivo conditions. The recommendation of this study is that the same experiment would be applicable for expression of the other form of this enzyme, SOD3, as well. More valuable information could probably be provided about the variety of the diseases caused by superoxide anions toxicities by intervention and application of the non-viral method for expressions of SOD1 and SOD3 enzymes.

Recent findings on the physiological function of DJ-1: Beyond Parkinson's disease

Several mutations in the gene coding for DJ-1 have been associated with early onset forms of parkinsonism. In spite of the massive effort spent by the scientific community in understanding the physiological role of DJ-1, a consensus on what DJ-1 actually does within the cells has not been reached, with several diverse functions proposed. At present, the most accepted function for DJ-1 is a neuronal protective role against oxidative stress. However, how exactly this function is exerted by DJ-1 is not clear. In recent years, novel molecular mechanisms have been suggested that may account for the antioxidant properties of DJ-1. In this review, we critically analyse the experimental evidence, including some very recent findings, supporting the purported neuroprotective role of DJ-1 through different mechanisms linked to oxidative stress handling, as well as the relevance of these processes in the context of Parkinson's disease.

Tauroursodeoxycholic Acid Improves the Survival and Function of Nigral Transplants in a Rat Model of Parkinson's Disease

There is accumulating evidence showing that the majority of cell death in neural grafts results from apoptosis when cells are implanted into the brain. Tauroursodeoxycholic acid (TUDCA), a taurine-conjugated hydrophilic bile acid, has been found to possess antiapoptotic properties. In the present study we have examined whether the supplementation of TUDCA to cell suspensions prior to transplantation can lead to enhanced survival of nigral grafts. We first conducted an in vitro study to examine the effects of TUDCA on the survival of dopamine neurons in serum-free conditions. The number of tyrosine hydroxylase (TH)-positive neurons in the TUDCA-treated cultures was significantly greater than that of control cultures 7 days in vitro. In addition, a terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) assay showed that the number of apoptotic cells in the TUDCA-treated cultures was dramatically smaller than that in the control cultures. In the transplantation study, a 50 μM concentration of TUDCA was added to the media when nigral tissue from Sprague-Dawley (SD) rats was trypsinized and dissociated. Two microliters of cell suspension containing TUDCA was then stereotaxically injected into the striatum of adult SD rats subjected to an extensive unilateral 6-hydroxydopamine lesion of the nigrastriatal dopamine pathway. At 2 weeks after transplantation, the rats that received a cell suspension with TUDCA exhibited a significant reduction in amphetamine-induced rotation scores when compared with pretransplantation value. There was a significant increase (approximately threefold) in the number of TH-positive cells in the neural grafts for the TUDCA-treated group when compared with the controls 6 weeks postgrafting. The number of apoptotic cells was much smaller in the graft areas in the TUDCA-treated groups than in the control group 4 days after transplantation. These data demonstrate that pretreatment of the cell suspension with TUDCA can reduce apoptosis and increase the survival of grafted cells, resulting in an improvement of behavioral recovery.

Effects of Surgical Anaesthesia on the Viability of Nigral Grafts in the Rat Striatum

Only a small proportion of dopamine neurons in nigral grafts typically survive transplantation into the adult striatum. Since many anaesthetics reduce blood flow and disturb a variety of brain metabolites, surgical anaesthesia may be one of the factors that compromise graft survival. Conversely, the lowered core body temperature induced by some anaesthetics might promote the survival of grafted cells by slowing their metabolism. In an initial screen, the widely-used surgical anaesthetic, equithesin, was found to reduce core temperature, mean arterial blood pressure, and to increase the partial pressure of oxygen in arterial blood without producing any significant alteration in arterial pH or the partial pressure of carbon dioxide. In the main experiment, rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal bundle received dopamine-rich embryonic nigral grafts injected into the deafferented neostriatum via previously implanted guide cannulae, which allowed comparison to be made of graft survival after transplantation into awake and in re-anaesthetised animals. There were no significant differences between groups in either the functional effects of the grafts to compensate amphetamine-induced rotation, or in the survival and growth of the grafts as measured in post mortem histology. We therefore conclude that anaesthesia per se is not a major contributory factor in the relatively poor survival of dopamine neurons following transplantation into the rat striatum.

Survival of Nigral Grafts within the Striatum of Marmosets with 6-Ohda Lesions Depends Critically on Donor Embryo Age

The study examined the importance of embryonic donor age for the survival of nigral grafts in 6-OHDA–lesioned marmosets. The issue as to whether donor age is critical for the survival of nigral grafts in primates is controversial, because several early reports suggested that relatively old tissue could survive transplantation and produce functional benefits in monkeys, in contrast to the restrictive time dependence observed in rodents. Embryonic marmoset donors embryos of three different ages were employed: 1) E74 (Carnegie stage 18-19); 2) E83-84 (Carnegie stage 23+); 3) E92-93 (foetal period). The nigral neurons derived from the ventral mesencephalon in the two older donor age groups did not survive well when grafted to the striatum of adult marmosets with unilateral 6-OHDA lesions. Although a few tyrosine hydroxylase (TH+) neurons could be identified by immunohistochemistry at graft sites in all recipients in older donor age groups, the numbers of surviving neurons in these were small, on average typically less than 100 TH+ cells. These small grafts were not sufficient to affect amphetamine-induced rotation. In contrast, many more TH+ cells typically survived transplantation in the recipients; of graft tissue derived from the youngest donors and amphetamine-induced rotation was significantly reduced in this group alone. The time course and extent of the reduction in rotation was remarkably similar to that observed in previous marmoset nigral graft studies, confirming the utility of amphetamine-induced rotation as a sensitive and reliable indicator of nigral graft function in this species. Considering these results and other recent evidence from monkey to monkey, human to rat, and human to human graft studies, the survival of embryonic nigral tissues derived from primate donors transplanted into the striatum does appear to be critically dependent on the age of the donor tissue.

Addition of Lateral Ganglionic Eminence to Rat Mesencephalic Grafts Affects Fiber Outgrowth but Does not Enhance Function

Addition of embryonic striatal tissue, usually as a combination of the lateral and medial ganglionic eminences, to intrastriatal mesencephalic grafts has previously been reported to enhance recovery of drug-induced rotational behavior in the host and to modify axonal fiber outgrowth from the grafted dopaminergic neurons. This study investigated the effects of adding (cografting) either lateral or medial ganglionic eminence tissue to embryonic mesencephalic grafts implanted intrastriatally, in rats with unilateral 6-hydroxydopamine lesions. The cografts did not exhibit increased survival or cell size of dopaminergic neurons when compared to transplants of mesencephalic tissue alone. Neither did recipients of cografts exhibit any enhancement of graft-induced recovery of function, when tested for drug-induced rotational behavior or forelimb function in the staircase test. However, cografts containing lateral ganglionic eminence displayed patches of dense tyrosine hydroxylase-immunoreactive fibers within the graft tissue. These patches largely coincided with patches in adjacent stained sections, which were rich in immunostaining for the striatal-specific marker dopamine- and cyclic AMP-regulated phosphoprotein-32 (DARPP-32). Such patches were not present in rats receiving cografts containing medial ganglionic eminence or mesencephalic tissue alone. Thus, it seems that the grafted dopaminergic neurons preferentially grow into the areas of the transplants containing lateral ganglionic eminence tissue. In summary, the results suggest that embryonic lateral ganglionic eminence exerts trophic effects on the outgrowth of dopaminergic axons, but does not enhance the behavioral effects of grafted dopaminergic neurons.

Molecular Etiology of Parkinson Disease: Recent Progress

Parkinson disease (PD) is one of the most widespread neurodegenerative disorders. In North America alone it affects 1 million people. It is a multifactorial disorder caused by genetic, various biological and environmental factors. One of the important features of PD is the dementia, which is believed to be due to the loss of dopaminergic neurons. In some cases the disease can be inherited as an autosomal dominant or recessive trait but in the majority of cases it is acquired. The biological causes of the disorder are unknown. The identification of mutations in the parkin gene in the autosomal recessive case and alpha-synuclein gene in autosomal dominant cases has opened a new avenue for studies to understand the basic biochemical mechanisms of pathogenesis. Although several types of treatments such as transplantation of cells that produce L-Dopa and direct gene delivery using adeno-associated viral vectors may correct animal models of PD, their usefulness in the human is not yet clear. A better understanding of the causes of neurodegeneration may lead to better therapies in the future.

Transcriptome analysis reveals transmembrane targets on transplantable midbrain dopamine progenitors

An important challenge for the continued development of cell therapy for Parkinson's disease (PD) is the establishment of procedures that better standardize cell preparations for use in transplantation. Although cell sorting has been an anticipated strategy, its application has been limited by lack of knowledge regarding transmembrane proteins that can be used to target and isolate progenitors for midbrain dopamine (mDA) neurons. We used a "FACS-array" approach to identify 18 genes for transmembrane proteins with high expression in mDA progenitors and describe the utility of four of these targets (Alcam, Chl1, Gfra1, and Igsf8) for isolating mDA progenitors from rat primary ventral mesencephalon through flow cytometry. Alcam and Chl1 facilitated a significant enrichment of mDA neurons following transplantation, while targeting of Gfra1 allowed for robust separation of dopamine and serotonin neurons. Importantly, we also show that mDA progenitors isolated on the basis of transmembrane proteins are capable of extensive, functional innervation of the host striatum and correction of motor impairment in a unilateral model of PD. These results are highly relevant for current efforts to establish safe and effective stem cell-based procedures for PD, where clinical translation will almost certainly require safety and standardization measures in order to deliver well-characterized cell preparations.

Copper and copper proteins in Parkinson's disease

Copper is a transition metal that has been linked to pathological and beneficial effects in neurodegenerative diseases. In Parkinson's disease, free copper is related to increased oxidative stress, alpha-synuclein oligomerization, and Lewy body formation. Decreased copper along with increased iron has been found in substantia nigra and caudate nucleus of Parkinson's disease patients. Copper influences iron content in the brain through ferroxidase ceruloplasmin activity; therefore decreased protein-bound copper in brain may enhance iron accumulation and the associated oxidative stress. The function of other copper-binding proteins such as Cu/Zn-SOD and metallothioneins is also beneficial to prevent neurodegeneration. Copper may regulate neurotransmission since it is released after neuronal stimulus and the metal is able to modulate the function of NMDA and GABA A receptors. Some of the proteins involved in copper transport are the transporters CTR1, ATP7A, and ATP7B and the chaperone ATOX1. There is limited information about the role of those biomolecules in the pathophysiology of Parkinson's disease; for instance, it is known that CTR1 is decreased in substantia nigra pars compacta in Parkinson's disease and that a mutation in ATP7B could be associated with Parkinson's disease. Regarding copper-related therapies, copper supplementation can represent a plausible alternative, while copper chelation may even aggravate the pathology.

Melatonin-based therapeutics for neuroprotection in stroke

The present review paper supports the approach to deliver melatonin and to target melatonin receptors for neuroprotection in stroke. We discuss laboratory evidence demonstrating neuroprotective effects of exogenous melatonin treatment and transplantation of melatonin-secreting cells in stroke. In addition, we describe a novel mechanism of action underlying the therapeutic benefits of stem cell therapy in stroke, implicating the role of melatonin receptors. As we envision the clinical entry of melatonin-based therapeutics, we discuss translational experiments that warrant consideration to reveal an optimal melatonin treatment strategy that is safe and effective for human application.

Cografting of carotid body cells improves the long-term survival, fiber outgrowth and functional effects of grafted dopaminergic neurons

AIMS

A major limiting factor for cell therapy in Parkinson's disease is that the survival of grafted dopaminergic neurons is very poor, which may be improved by administration of GDNF, for which the carotid body is a good source.

MATERIALS & METHODS

Rats with total unilateral dopaminergic denervation were grafted with a cell suspension of rat dopaminergic neuroblasts with or without cell aggregates from the rat carotid body. At 1, 2 and 3 months after grafting, the rats were tested in the cylinder and the rotometer and killed 4 months after grafting.

RESULTS

We observed that the survival of dopaminergic neurons and graft-derived dopaminergic innervation were higher in rats that received mixed grafts. Both grafted groups showed complete recovery in the amphetamine-induced rotation test. However, rats with cografts performed significantly better in the cylinder test.

CONCLUSION

Cografting of carotid body cells may constitute a useful strategy for cell therapy in Parkinson's disease.

Functional aspects of redox control during neuroinflammation

Neuroinflammation is a CNS reaction to injury in which some severe pathologies, regardless of their origin, converge. The phenomenon emphasizes crosstalk between neurons and glia and reveals a complex interaction with oxidizing agents through redox sensors localized in enzymes, receptors, and transcription factors. When oxidizing pressures cause reversible molecular changes, such as minimal or transitory proinflammatory cytokine overproduction, redox couples provide a means of translating the presence of reactive oxygen or nitrogen species into useful signals in the cell. Additionally, thiol-based redox sensors convey information about localized changes in redox potential induced by physiologic or pathologic situations. They are susceptible to oxidative changes and become key events during neuroinflammation, altering the course of a signaling response or the behavior of specific transcription factors. When oxidative stress augments the pressure on the intracellular environment, the effective reduction potential of redox pairs diminishes, and cell signaling shifts toward proinflammatory and proapoptotic signals, creating a vicious cycle between oxidative stress and neuroinflammation. In addition, electrophilic compounds derived from the oxidative cascade react with key protein thiols and interfere with redox signaling. This article reviews the relevant functional aspects of redox control during the neuroinflammatory process.

The Clinical Application of Ozonetherapy

The reader may be eager to examine in which diseases ozonetherapy can be proficiently used and she/he will be amazed by the versatility of this complementary approach (Table 9 1). The fact that the medical applications are numerous exposes the ozonetherapist to medical derision because superficial observers or sarcastic sceptics consider ozonetherapy as the modern panacea. This seems so because ozone, like oxygen, is a molecule able to act simultaneously on several blood components with different functions but, as we shall discuss, ozonetherapy is not a panacea. The ozone messengers ROS and LOPs can act either locally or systemically in practically all cells of an organism. In contrast to the dogma that “ozone is always toxic”, three decades of clinical experience, although mostly acquired in private clinics in millions of patients, have shown that ozone can act as a disinfectant, an oxygen donor, an immunomodulator, a paradoxical inducer of antioxidant enzymes, a metabolic enhancer, an inducer of endothelial nitric oxide synthase and possibly an activator of stem cells with consequent neovascularization and tissue reconstruction.

Protection of dopamine neurons by bone marrow stromal cells

Transplantation of bone marrow stromal cells (BMSC) has recently been demonstrated to provide neuroprotection in animal models of brain injuries such as ischemia and trauma. The present study was undertaken to explore whether BMSC can promote the survival of dopamine (DA) neurons in neuronal insult models in vitro. We also examined whether BMSC can increase the survival rate of embryonic DA neurons grafted into the striatum of a rat model of Parkinson's disease (PD). Treatment with conditioned media derived from BMSC cultures was found to significantly prevent the death of DA neurons in in vitro cell injury models such as serum deprivation and exposure to the neurotoxin 6-OHDA. In a transplantation study, we also found that the survival of grafted DA cells was significantly enhanced by treating donor cells with the conditioned media at the steps of both cell dissociation and implantation. The results suggest that BMSC may secrete diffusible factors able to protect DA neurons against neuronal injuries. Indeed, BMSC expressed mRNA encoding brain-derived neurotrophic factor, fibroblast growth factor-2 and glial cell line-derived neurotrophic factor, all of which have previously been shown to exhibit potent neurotrophic effects on DA cells. Enzyme-linked immunosorbent assay revealed that the cells release these growth factors into culture media. The present data indicate that BMSC may be a potential donor source of cell-based regenerative therapy for PD where the progressive loss of the midbrain DA neurons takes place.

SOD1 overexpression alters ROS production and reduces neurotoxic inflammatory signaling in microglial cells

Activation of the oxidative burst is one of the earliest biochemical events in microglial activation, but it is not understood yet how free radicals participate in inflammatory signaling. To determine the role that specific reactive oxygen species play in microglial activation, the levels of SOD1 were manipulated in N9 murine microglia. Stable overexpression of SOD1 caused significant decreases in superoxide and nitric oxide production, with concurrent increases in hydrogen peroxide following LPS. However, LPS-induced activation of NFkappaB, and release of TNFalpha and IL-6 were significantly attenuated in SOD1 overexpressing cells, as was the ability of microglia to induce toxicity in cultured neurons. Conversely, acute inhibition of SOD1 with disulfiram was associated with increased nitric oxide and cytokine release, and increased neurotoxicity. Together, these data suggest that superoxide radicals in microglia play important roles in directing redox-sensitive inflammatory signaling and initiating neurotoxic inflammation.

New therapeutic approaches to Parkinson's disease including neural transplants

Parkinson's disease (PD) is a common neurodegenerative disorder of the brain and typically presents with a disorder of movement. The core pathological event underlying the condition is the loss of the dopaminergic nigrostriatal pathway with the formation of alpha-synuclein positive Lewy bodies. As a result, drugs that target the degenerating dopaminergic network within the brain work well at least in the early stages of the disease. Unfortunately, with time these therapies fail and produce their own unique side-effect profile, and this, coupled with the more diffuse pathological and clinical findings in advancing disease, has led to a search for more effective therapies. In this review, the authors will briefly discuss the emerging new drug therapies in PD before concentrating on a more detailed discussion on the state of cell therapies to cure PD.

Evaluation of [123I]IBZM pinhole SPECT for the detection of striatal dopamine D2 receptor availability in rats

Single photon emission computed tomography (SPECT) and MRI coregistration have been assessed to characterize striatal dopamine D2/D3 receptor (D2/D3R) availability in rats following injection of the D2 and D3R radioligand [123I] iodobenzamide ([123I]IBZM). High-resolution SPECT data were obtained with a pinhole collimator. In order to precisely estimate brain regions of low radioligand uptake, SPECT images were coregistered onto a MRI template with high accuracy (maximum mismatch 1.1 mm). To evaluate an adequate dose of radioligand to be administered without exceeding the radioligand-to-receptor occupancy >5% and to define an appropriate time period for image acquisition, three untreated groups of animals received 29.6, 37, and 44.4 MBq of [123I]IBZM and underwent five consecutive SPECT acquisitions lasting 64 min each. Ratio calculations between specific striatal radioligand uptake and nondisplaceable cerebellar uptake revealed a secular equilibrium between 75 and 355 min post-tracer application in all three animal groups. Consequently, since the highest regional uptake values were obtained in the animal group receiving 44.4 MBq [123I]IBZM, this injection dose was considered to be appropriate. Finally, the capacity of the imaging method to detect distinct severity levels of striatal dopamine D2/D3 receptor loss was tested in a low, medium, and high dose quinolinic acid (QA) animal model of Huntington's disease. Motor impairment indicative of striatal dysfunction was monitored using amphetamine-induced rotational behavior and locomotor activity. Loss of striatal D2/D3R bearing medium-sized spiny neurons was assessed by DARPP-32 immunohistochemistry and compared to [123I]IBZM binding. Optical density measures of DARPP-32 immunohistochemistry demonstrated QA dose-dependent mild to subtotal unilateral striatal lesions ranging from 29.4% to 96.9% when compared to the nonlesioned side. Linear regression analysis showed that measurements of striatal DARPP-32 optical density and striatal [123I]IBZM uptake of the lesioned side were highly correlated (r2=0.83; P<0.001) whereas correlation with locomotor activity was less tight (r2=0.23; P<0.05; amphetamine-induced rotational behavior was not significantly correlated). This is the first study to demonstrate that in vivo [123I]IBZM SPECT and MRI coregistration are highly sensitive and, in contrast to behavioral measures, accurately detect mild to subtotal striatal lesions by measuring loss of D2/D3R availability. SPECT-MRI-based estimation of regional [123I]IBZM uptake provides a cost effective and widely available in vivo imaging technique for assessing striatal integrity in animal studies.

Gene therapy in Parkinson?s disease

Gene therapy in Parkinson's disease appears to be at the brink of the clinical study phase. Future gene therapy protocols will be based on a substantial amount of preclinical data regarding the use of ex vivo and in vivo genetic modifications with the help of viral or non-viral vectors. To date, the supplementation of neurotrophic factors and substitution for the dopaminergic deficit have formed the focus of trials to achieve relief in animal models of Parkinson's disease. Newer approaches include attempts to influence detrimental cell signalling pathways and to inhibit overactive basal ganglia structures. Nevertheless, current models of Parkinson's disease do not mirror all aspects of the human disease, and important issues with respect to long-term protein expression, choice of target structures and transgenes and safety remain to be solved. Here, we thoroughly review available animal data of gene transfer in models of Parkinson's disease.

The ability of grafted human sympathetic neurons to synthesize and store dopamine: a potential mechanism for the clinical effect of sympathetic neuron autografts in patients with Parkinson's disease

We have investigated the potential of autologous sympathetic neurons as a donor for cell therapy of Parkinson's disease (PD). Our recent study demonstrated that sympathetic neuron autografts increase the duration of levodopa-induced "on" periods with consequent reduction in the percent time spent in "off" phase. We also found that human sympathetic neurons grown in culture have the ability to convert exogenous levodopa to dopamine and to store the synthesized dopamine. This may explain the clinically observed prolongation in the duration of levodopa effects. To further analyze the mechanism for the graft-mediated effect, the present study investigated the metabolic function of human sympathetic ganglionic neurons xenografted into the dopamine (DA)-denervated striatum of rats by monitoring striatal levels of DA and its primary metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), after systemic administration of levodopa. We also explored whether the graft-mediated effect above may last in four PD patients who had been given the grafts and followed for 12-36 months postgrafting. Clinical evaluations showed that an increase in the duration of levodopa-induced "on" phase is detected during a follow-up period of 12-36 months postgrafting in all the four patients tested. Accordingly, the percent time spent in "off" phase exhibited a 30-40% reduction as compared to the pregrafting values. The animal experiment showed that a significant increase in striatal DA levels is noted after systemic levodopa treatment, and that the DA levels remain high for longer periods of time in the grafted rats than in control animals. When given reserpine pretreatment, the levodopa-induced rise of striatal DA levels was significantly attenuated with concomitant increase in DOPAC levels. Histological examinations demonstrated that the grafts contain some tyrosine hydroxylase (TH)-positive cells. These cells were also found to express aromatic-l-amino acid decarboxylase (AADC) and vesicular monoamine transporter-2 (VMAT), both of which are important molecules for the synthesis and the storage of DA, respectively. These results indicate that grafted sympathetic neurons can provide a site for both the conversion of exogenous levodopa to DA and the storage of the synthesized DA in the DA-denervated striatum, explaining a mechanism by which sympathetic neuron autografts can increase the duration of levodopa-induced "on" phase in PD patients.

On the selectivity of superoxide dismutase mimetics and its importance in pharmacological studies

The list of pathophysiological conditions associated with the overproduction of superoxide expands every day. Much of the knowledge compiled on the role of this radical in disease has been gathered using the native superoxide dismutase enzyme and, more recently, by the use of superoxide dismutase knockout models or transgenic models that overexpress the various isoforms of the enzyme. Although the native enzyme has shown promising anti-inflammatory properties in both preclinical and clinical studies, there were drawbacks and issues associated with its use as a therapeutic agent and pharmacological tool. Based on the concept that removal of superoxide modulates the course of inflammation, synthetic, low-molecular-weight mimetics of the superoxide dismutase enzymes that could overcome some of the limitations associated with the use of the native enzyme have been designed. In this review, we will discuss the advances made using various superoxide dismutase mimetics that led to the proposal that superoxide (and/or the product of its interaction with nitric oxide, peroxynitrite) is an important mediator of inflammation, and to the conclusion that superoxide dismutase mimetics can be utilized as therapeutic agents in diseases of various etiologies. The importance of the selectivity of such compounds in pharmacological studies will be discussed.

Melatonin-secreting pineal gland: a novel tissue source for neural transplantation therapy in stroke

Chronic systemic melatonin treatment attenuates abnormalities produced by occlusion of middle cerebral artery (MCA) in adult rats. Because the pineal gland secretes high levels of melatonin, we examined in the present study whether transplantation of pineal gland exerted similar protective effects in MCA-occluded adult rats. Animals underwent same-day MCA occlusion and either intrastriatal transplantation of pineal gland (harvested from 2-month-old rats) or vehicle infusion. Behavioral tests (from day of surgery to 3 days posttransplantation) revealed that transplanted stroke rats displayed significantly less motor asymmetrical behaviors than vehicle-infused stroke rats. Histological analysis at 3 days posttransplantation revealed that transplanted stroke rats had significantly smaller cerebral infarction than vehicle-infused rats. Additional experiments showed that pinealectomy affected transplantation outcome, in that transplantation of pineal gland only protected against stroke-induced deficits in stroke animals with intact pineal gland, but not in pinealectomized stroke rats. Interestingly, nonpinealectomized vehicle-infused stroke rats, as well as pinealectomized transplanted stroke rats, had significantly lower melatonin levels in the cerebrospinal fluid than nonpinealectomized transplanted stroke rats. We conclude that intracerebral transplantation of pineal gland, in the presence of host intact pineal gland, protected against stroke, possibly through secretion of melatonin.

Gene therapy for experimental brain tumors using a xenogenic cell line engineered to secrete hIL-2

Local delivery of cytokines has been shown to have a potent anti-tumor activity against a wide range of malignant brain tumors. In this study, we examined the feasibility and efficacy of using a rat endothelial cell line (NTC-121) transfected with the human interleukin-2 (IL-2) gene in treating experimental murine CNS tumors. The NTC-121 cells were injected intracranially in C57BL/6 mice (N = 10/group) along with non-irradiated, non-transfected B16/F10 (wild type) melanoma cells. Sixty percent of mice treated with IL-2 (p < 0.001 vs. control) were long-term survivors (LTS) of > 120 days. Control animals that received only wild type cells had a median survival of 18 days (range 15-20). Histopathological examination of brains from animals sacrificed at different times showed no tumor growth in the non-irradiated NTC-121 group, moderate (1-2 mm) tumor growth in the irradiated group, and gross tumor invasion (>2 mm) and tissue necrosis in the control group. Moreover, animals treated with IL-2 showed an accumulation of CD8+ T cells around the site of the injected tumor. The use of a xenogenic cell line to deliver hIL-2 stimulates a strong immunologic cytotoxic anti-tumor response that leads to significant prolongation of survival in mice challenged with the B16/F10 intracranial melanoma tumor. Our findings demonstrate that the use of a xenogenic cell line can provide a potent vehicle for the delivery of gene therapy and may therefore represent a new approach for brain tumor therapy.

The release of excitatory amino acids, dopamine, and potassium following transplantation of embryonic mesencephalic dopaminergic grafts to the rat striatum, and their effects on dopaminergic neuronal survival in vitro

A major limitation to the effectiveness of grafts of fetal ventral mesencephalic tissue for parkinsonism is that about 90-95% of grafted dopaminergic neurones die. In rats, many of the cells are dead within 1 day and most cell death is complete within 1 week. Our previous results suggest that a major cause of this cell death is the release of toxins from the injured CNS tissue surrounding the graft, and that many of these toxins have dissipated within 1 h of inserting the grafting cannula. In the present experiments we measured the change over time in the concentration of several potential toxins around an acutely implanted grafting cannula. We also measured the additional effect of injecting suspensions of embryonic mesencephalon, latex microspheres, or vehicle on these concentrations. Measurements of glutamate, aspartate, and dopamine by microdialysis showed elevated levels during the first 20-60 min, which then declined to baseline. In the first 20 min glutamate levels were 10.7 times, aspartate levels 5 times, and dopamine levels 24.3 times baseline. Potassium levels increased to a peak of 33 +/- 10.6 mM 4-5 min after cannula insertion, returning to baseline of <5 mM by 30 min. Injection of cell suspension, latex microspheres, or vehicle had no significant effect on these levels. We then assayed the effect of high concentrations of glutamate, aspartate, dopamine, and potassium on dopaminergic neuronal survival in E14 ventral mesencephalic cultures. In monolayer cultures only dopamine at 200 microM showed toxicity. In three-dimensional cultures only the combination of raised potassium, dopamine, glutamate, and aspartate together decreased dopaminergic neuronal survival. We conclude that toxins other than the ones measured are the main cause of dopaminergic cell death after transplantation, or the effects of the toxins measured are enhanced by anoxia and metabolic challenges affecting newly inserted grafts.

Characterisation of cell damage and death in embryonic mesencephalic tissue: a study on ultrastructure, vital stains and protease activity

Dissociated embryonic ventral mesencephalic tissue is a source of dopaminergic neurones in both cell culture and neural transplantation studies. Around 90% of grafted dopaminergic neurones die within 1 week after transplantation. Little is known about when the cell death is triggered and what forms of cell death predominate. Using electron microscopy, we characterised ultrastructural changes in dissected embryonic day 14 rat mesencephalic tissue before and after tissue dissociation. In addition, cell viability was evaluated using Trypan Blue and Hoechst/Ethidium Homodimer. Several cells exhibited leaky outer membranes (permitting entry of vital stains) and ultrastructural degeneration already immediately after the mesencephalon was dissected, and before it was mechanically disrupted. After 2 h at room temperature, 90% of the remaining cells had intact outer membranes. However, when estimating cells lost acutely in the tissue dissociation, in addition to cells exhibiting condensed chromatin and organellar changes, we suggest that only around 14% of the cells initially dissected in the mesencephalic tissue pieces remained healthy after 2 h. There was a peak in calpain activity (specific cleavage of fodrin) immediately following tissue dissociation, and it subsided during the next few hours. Caspase-3 activity was initially low, but increased almost 20-fold 4 h after tissue disruption. Interestingly, extensive degradation of caspase-3 occurred already directly after dissection and was at least partly calpain-dependent. Our data suggest that, in addition to cells undergoing primary necrosis, some cells undergo apoptotic or related changes soon after tissue harvesting, and eventually undergo a secondary necrosis. In summary, embryonic mesencephalic cells exhibit multiple degenerative changes very early on in the neural transplant/tissue culture preparation protocol.

Comparison between survival of lazaroid-treated embryonic nigral neurons in cell suspensions, cultures and transplants

Death of transplanted dopaminergic neurons is induced both during preparation of donor tissue and after intrastriatal grafting. Oxidative stress is thought to be partly responsible for this cell death. In the present study we compared the effects of three lipid peroxidation inhibitors, the lazaroids Tirilazad mesylate, U-83836E and U-101033, on survival of embryonic mesencephalic neurons in different paradigms. The lazaroids were equally potent in preventing serum deprivation-induced death of cultured dopaminergic neurons. In a second set of experiments, mesencephalic suspensions were pretreated with lazaroids and cell survival was analyzed immediately after dissociation, after 2 or 24 h in culture or after intrastriatal transplantation. Lazaroid pretreatment failed to protect mesencephalic neurons in the in vitro paradigms and U-101033E did not protect grafted dopaminergic neurons in contrast to the neuroprotective effects previously reported for U-83836E and Tirilazad. Pretreatment with the iron chelator deferoxamine mesylate did not protect cultured or grafted dopaminergic neurons, nor did it improve neuronal survival in the serum deprivation model. U-83836E and U-101033E, but not Tirilazad, prevented cell death induced by the pro-oxidant tert-butyl hydroperoxide in suspensions. In a final experiment, we found that systemic treatment of the graft recipient rat with Tirilazad mesylate (before and during the first 3 days after grafting) improved survival of transplanted dopaminergic neurons to 180% of control values. Our results show that systemic treatment with a lipid peroxidation inhibitor for 3 days can promote graft survival, but also highlights the poor correlation between neuroprotective effect of pharmacological compounds in vitro and in grafts.

Cellular replacement therapy for Parkinson's disease--where we are today?

The concept of replacing lost dopamine neurons in Parkinson's disease using mesencephalic brain cells from fetal cadavers has been supported by over 20 years of research in animals and over a decade of clinical studies. The ambitious goal of these studies was no less than a molecular and cellular "cure" for Parkinson's disease, other neurodegenerative diseases, and spinal cord injury. Much research has been done in rodents, and a few studies have been done in nonhuman primate models. Early uncontrolled clinical reports were enthusiastic, but the outcome of the first randomized, double blind, controlled study challenged the idea that dopamine replacement cells can cure Parkinson's disease, although there were some significant positive findings. Were the earlier animal studies and clinical reports wrong? Should we give up on the goal? Some aspects of the trial design and implantation methods may have led to lack of effects and to some side effects such as dyskinesias. But a detailed review of clinical neural transplants published to date still suggests that neural transplantation variably reverses some aspects of Parkinson's disease, although differing methods make exact comparisons difficult. While the randomized clinical studies have been in progress, new methods have shown promise for increasing transplant survival and distribution, reconstructing the circuits to provide dopamine to the appropriate targets and with normal regulation. Selected promising new strategies are reviewed that block apoptosis induced by tissue dissection, promote vascularization of grafts, reduce oxidant stress, provide key growth factors, and counteract adverse effects of increased age. New sources of replacement cells and stem cells may provide additional advantages for the future. Full recovery from parkinsonism appears not only to be possible, but a reliable cell replacement treatment may finally be near.

Role of superoxide dismutases in oxidative damage and neurodegenerative disorders

In recent years, oxidative stress has been implicated in a variety of degenerative processes, diseases, and syndromes. Some of these include atherosclerosis, myocardial infarction, stroke, and ischemia/reperfusion injury; chronic and acute inflammatory conditions such as wound healing; central nervous system disorders such as forms of familial amyotrophic lateral sclerosis (ALS) and glutathione peroxidase-linked adolescent seizures; Parkinson's disease and Alzheimer's dementia; and a variety of other age-related disorders. Among the various biochemical events associated with these conditions, emerging evidence suggests the formation of superoxide anion and expression/activity of its endogenous scavenger, superoxide dismutase (SOD), as a common denominator. This review summarizes the function of SOD under normal physiological conditions as well as its role in the cellular and molecular mechanisms underlying oxidative tissue damage and neurological abnormalities. Experimental evidence from laboratory animals that either overexpress (transgenics) or are deficient (knockouts) in antioxidant enzyme/protein levels and the genetic SOD mutations observed in some familial cases of ALS are also discussed.

Neural transplantation for treatment of Parkinson's disease

Neural transplantation has emerged as an efficacious experimental treatment for CNS disorders, especially Parkinson's disease. However, logistical and ethical issues impede large-scale clinical trials. To this end, alternatives to human fetal cells as donor cell grafts have been examined, including xenografts, stem cells, genetically engineered cells, immortalized cell lines, or paraneural cells that secrete specific neurotrophic or growth factors. Accumulating evidence also suggests that exogenous treatment with neurotrophic or growth factors, immunosuppressants, free radical scavengers, and anti-apoptotic agents can enhance survival and functional effects of the grafts. This article will review recent studies demonstrating the potential of these alternative cell graft sources and novel drugs for treating Parkinson's disease.

Role of free radicals in the neurodegenerative diseases: therapeutic implications for antioxidant treatment

Free radicals and other so-called 'reactive species' are constantly produced in the brain in vivo. Some arise by 'accidents of chemistry', an example of which may be the leakage of electrons from the mitochondrial electron transport chain to generate superoxide radical (O2*-). Others are generated for useful purposes, such as the role of nitric oxide in neurotransmission and the production of O2*- by activated microglia. Because of its high ATP demand, the brain consumes O2 rapidly, and is thus susceptible to interference with mitochondrial function, which can in turn lead to increased O2*- formation. The brain contains multiple antioxidant defences, of which the mitochondrial manganese-containing superoxide dismutase and reduced glutathione seem especially important. Iron is a powerful promoter of free radical damage, able to catalyse generation of highly reactive hydroxyl, alkoxyl and peroxyl radicals from hydrogen peroxide and lipid peroxides, respectively. Although most iron in the brain is stored in ferritin, 'catalytic' iron is readily mobilised from injured brain tissue. Increased levels of oxidative damage to DNA, lipids and proteins have been detected by a range of assays in post-mortem tissues from patients with Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis, and at least some of these changes may occur early in disease progression. The accumulation and precipitation of proteins that occur in these diseases may be aggravated by oxidative damage, and may in turn cause more oxidative damage by interfering with the function of the proteasome. Indeed, it has been shown that proteasomal inhibition increases levels of oxidative damage not only to proteins but also to other biomolecules. Hence, there are many attempts to develop antioxidants that can cross the blood-brain barrier and decrease oxidative damage. Natural antioxidants such as vitamin E (tocopherol), carotenoids and flavonoids do not readily enter the brain in the adult, and the lazaroid antioxidant tirilazad (U-74006F) appears to localise in the blood-brain barrier. Other antioxidants under development include modified spin traps and low molecular mass scavengers of O2*-. One possible source of lead compounds is the use of traditional remedies claimed to improve brain function. Little is known about the impact of dietary antioxidants upon the development and progression of neurodegenerative diseases, especially Alzheimer's disease. Several agents already in therapeutic use might exert some of their effects by antioxidant action, including selegiline (deprenyl), apomorphine and nitecapone.

Gene therapy for Parkinson's disease

Significant progress has been made in the field of gene therapy for Parkinson's disease (PD). Successful vehicles for gene transfer into the central nervous system have been developed and clinical efficacy and safety have both been shown in various animal models of PD. Further optimisation of dosing, timing and location of gene therapy delivery as well as the ability to regulate and prolong gene expression will be important for the commencement of human trials. Current gene therapy models for PD have focused on two treatment strategies. One is the replacement of biosynthetic enzymes for dopamine synthesis and the second strategy is the addition of neurotrophic factors for protection and restoration of dopaminergic neurones. Concepts of neuroprotection and restoration of the nigrostriatal pathway will become important themes for future genetic treatment strategies for PD and may include, in addition to neurotrophic factors, genes to prevent apoptosis or detoxify free radical species. This review will highlight the recent literature on gene therapy for PD and summarise general approaches to gene therapy.

Brain engraftment of autologous macrophages transduced with a lentiviral flap vector: an approach to complement brain dysfunctions

Transplantation of ex vivo gene-corrected autologous cells represents an attractive therapeutic approach for brain diseases. Among the cells of the central nervous system, brain macrophages are promising candidates due to their role in tissue homeostasis and their implication in several neurological diseases. Up to now, gene transfer into macrophages has proven difficult by most currently available gene delivery methods. We describe herein, an efficient transduction of rat bone marrow-derived and brain macrophages with an HIV-1-derived vector containing a central DNA flap and encoding the GFP reporter gene (TRIP-DeltaU3-GFP). In primary cultures of macrophages our results show that more than 90% of the cells were transduced by the TRIP vector and that GFP expression remained stable for 1 month without cytopathic effect. In vivo, transplants of transduced macrophages into the striatum of adult rats exhibited long-term expression of GFP up to 3 months. Transduced macrophages were observed around the brain injection site and exhibited the brain macrophage/microglia phenotype. There was no significant sign of astrogliosis around the graft. These results confirm the potential of lentiviral vectors for efficient and stable ex vivo transduction of macrophages. Moreover, transduced autologous macrophages appear as a valuable vehicle for long-term and localized gene expression into the brain.

Cell survival and clinical outcome following intrastriatal transplantation in Parkinson disease

Intrastriatal transplantation of embryonic dopaminergic neurons is currently explored as a restorative cell therapy for Parkinson disease (PD). Clinical results have varied, probably due to differences in transplantation methodology and patient selection. In this review, we assess clinical trials and autopsy findings in grafted PD patients and suggest that a minimum number of surviving dopaminergic neurons is required for a favorable outcome. Restoration of [18F]-fluorodopa uptake in the putamen to about 50% of the normal mean seems necessary for moderate to marked clinical benefit to occur. Some studies indicate that this may require mesencephalic tissue from 3-5 human embryos implanted into each hemisphere. The volume, density and pattern of fiber outgrowth and reinnervation, as well as functional integration and dopamine release. are postulated as additional important factors for an optimal clinical outcome. For neural transplantation to become a feasible therapeutic alternative in PD, graft survival must be increased and the need for multiple donors of human embryonic tissue substantially decreased or alternate sources of donor tissue developed. Donor cells derived from alternative sources should demonstrate features comparable to those associated with successful implantation of human embryonic tissue before clinical trials are considered.

Effects of immunosuppressive treatment on host responses against intracerebral porcine neural tissue xenografts in rats

BACKGROUND

Embryonic xenogeneic neural tissue is an alternative for transplantation in Parkinson's disease, but immune responses limit the application. The aims of this study were to enhance the in vitro viability rates by donor tissue pretreatment; to compare the efficacy of cyclosporine A (CsA) and tacrolimus (FK) in inhibiting xenograft rejection in rats; to evaluate additional inductive therapy with prednisolone (PRE) or mycophenolate mofetil (MMF).

METHODS

Tirilazad (a lipid peroxidase inhibitor) or FK and acYVAD-cmk (a caspase inhibitor), were added to embryonic porcine ventral mesencephalic tissue and viability was assessed in vitro. Tirilazad-treated tissue was grafted to the striatum of rats that were either left untreated or immunosuppressed with FK (1 mg/kg) or CsA (15 mg/kg) alone or in combination with a 2-week PRE (20 mg/kg) or MMF (40 mg/kg) induction course. Xenograft survival and host responses were determined using immunohistochemistry.

RESULTS

Pretreatment with tirilazad enhanced tissue survival in vitro. After transplantation into untreated controls, there was no graft survival at twelve weeks. Neural cell counts were significantly improved in immunosuppressed recipients, but there were no differences between the treatment groups. Additional inductive treatment reduced the infiltration with CD4+ and CD8+ cells, and macrophage infiltration was reduced compared with animals given CsA or FK alone.

CONCLUSION

Pretreatment of the donor tissue with free-radical scavengers reduces cell loss caused by tissue trauma. Porcine neural tissue xenografts survive significantly better in animals immunosuppressed with either FK or CsA. Additional inductive treatment with PRE or MMF reduced the infiltration of host cells into the xenografts.

Increased superoxide dismutase and Down's syndrome

The enzyme superoxide dismutase (SOD) is a constitutive enzyme coded by a gene located in Chromosome 21 (21q22.1). Thus, the tissues from patients with trisomy 21 contain 50% more SOD activity. It is often suggested that the increased SOD content in the cells of Down's syndrome patients is responsible for many of the neurological symptoms of this disease. This hypothesis is not supported by most of the available data. In this paper we discuss why the increased SOD activity should not influence neuronal function and propose, instead, that the main problem may be an overexpression of other genes also located in chromosome 21 such as the beta amyloid precursor, as well as oncogenes and other Down's syndrome-related genes. We also propose that the increased SOD may be, instead, responsible for the increased incidence of Down's syndrome in children of older women. The augmented antioxidant protection resulting from an extra copy of chromosome 21 may, with time, selectively protect human oocytes from apoptosis, increasing their proportion with age, explaining the higher incidence of this disease.

Visualization, direct isolation, and transplantation of midbrain dopaminergic neurons

To visualize and isolate live dopamine (DA)-producing neurons in the embryonic ventral mesencephalon, we generated transgenic mice expressing green fluorescent protein (GFP) under the control of the rat tyrosine hydroxylase gene promoter. In the transgenic mice, GFP expression was observed in the developing DA neurons containing tyrosine hydroxylase. The outgrowth and cue-dependent guidance of GFP-labeled axons was monitored in vitro with brain culture systems. To isolate DA neurons expressing GFP from brain tissue, cells with GFP fluorescence were sorted by fluorescence-activated cell sorting. More than 60% of the sorted GFP(+) cells were positive for tyrosine hydroxylase, confirming that the population had been successfully enriched with DA neurons. The sorted GFP(+) cells were transplanted into a rat model of Parkinson's disease. Some of these cells survived and innervated the host striatum, resulting in a recovery from Parkinsonian behavioral defects. This strategy for isolating an enriched population of DA neurons should be useful for cellular and molecular studies of these neurons and for clinical applications in the treatment of Parkinson's disease.

Superoxide dismutase activity in organotypic midbrain-striatum co-cultures is associated with resistance of dopaminergic neurons to excitotoxicity

We have previously demonstrated that dopaminergic neurons in midbrain-striatum slice co-cultures are more resistant to NMDA cytotoxicity than the same neuronal population in single midbrain slice cultures. Here, we show that dopaminergic neurons in midbrain-striatum co-cultures also exhibit resistance to the cytotoxicity of nitric oxide donors, 2,2'-(hydroxynitrosohydrazono)bis-ethanamine (NOC-18) and 3-morpholinosydnonimine (SIN-1). The cytotoxicity of NMDA (30 microM) in single cultures was significantly attenuated by the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine (100 microM), whereas the toxicity in co-cultures was not. The levels of tyrosine residue nitration of tyrosine hydroxylase, a hallmark of the occurence of peroxynitrite anion in dopaminergic neurons, were lower in co-cultures than those in single cultures. Single cultures and co-cultures did not show appreciable differences in the number or distribution of NOS-containing neurons as assessed by NADPH diaphorase histochemistry. On the other hand, midbrain slices cultured with striatal slices showed higher levels of superoxide dismutase (SOD) activity as well as increased protein levels of Cu,Zn-SOD, than midbrain slices cultured alone. These results suggested that the generation of NO is involved in NMDA cytotoxicity on dopaminergic neurons, and that increased activity of SOD in co-cultures renders dopaminergic neurons resistant to NMDA cytotoxicity by preventing the formation of peroxynitrite.