Brain implantations of engineered GABA-releasing cells suppress tremor in an animal model of Parkinsonism

Immortalization Reversibility in the Context of Cell Therapy Biosafety

Immortalization (genetically induced prevention of replicative senescence) is a promising approach to obtain cellular material for cell therapy or for bio-artificial organs aimed at overcoming the problem of donor material shortage. Immortalization is reversed before cells are used in vivo to allow cell differentiation into the mature phenotype and avoid tumorigenic effects of unlimited cell proliferation. However, there is no certainty that the process of de-immortalization is 100% effective and that it does not cause unwanted changes in the cell. In this review, we discuss various approaches to reversible immortalization, emphasizing their advantages and disadvantages in terms of biosafety. We describe the most promising approaches in improving the biosafety of reversibly immortalized cells: CRISPR/Cas9-mediated immortogene insertion, tamoxifen-mediated self-recombination, tools for selection of successfully immortalized cells, using a decellularized extracellular matrix, and ensuring post-transplant safety with the use of suicide genes. The last process may be used as an add-on for previously existing reversible immortalized cell lines.

Blockade of adenosine A2A receptors inhibits Tremulous Jaw Movements as well as expression of zif-268 and GAD65 mRNAs in brain motor structures

Tremor is one of the motor symptoms of Parkinson's disease (PD), present also in neuroleptic-induced parkinsonism. Tremulous Jaw Movements (TJMs) are suggested to be a well-validated rodent model of PD resting tremor. TJMs can be induced by typical antipsychotics and are known to be reduced by different drugs, including adenosine A_2A receptor antagonists. The aim of the present study was to search for brain structures involved in the tremorolytic action of SCH58261, a selective A_2A receptor antagonist, in TJMs induced by subchronic pimozide. Besides TJMs, we evaluated in the same animals the expression of zif-268 mRNA (neuronal responsiveness marker), and mRNA levels for glutamic acid decarboxylase 65-kDa isoform (GAD65) and vesicular glutamate transporters 1 and 2 (vGluT1/2) in selected brain structures, as markers of GABAergic and glutamatergic neurons, respectively. We found that SCH58261 reduced the pimozide-induced TJMs. Pimozide increased the zif-268 mRNA level in the striatum, nucleus accumbens (NAc) core, and substantia nigra pars reticulata (SNr). Additionally, it increased GAD65 mRNA in the striatum and SNr, and vGluT2 mRNA levels in the subthalamic nucleus (STN). A positive correlation between zif-268, GAD65 and vGluT2 mRNAs and TJMs was found. SCH58261 reversed the pimozide-increased zif-268 mRNA in the striatum and NAc core and GAD65 mRNA in the striatum and SNr. In contrast, SCH58261 did not influence vGluT2 mRNA in STN. The present study suggests an importance of the striato-subthalamo-nigro-thalamic circuit in neuroleptic-induced TJMs. The tremorolytic effect of A_2A receptor blockade seems to involve this circuit bypassing, however, STN.

Involvement of adenosine A1 and A2A receptors on guanosine-mediated anti-tremor effects in reserpinized mice

Parkinson's disease (PD) signs and symptoms regularly include tremor. Interestingly, the nucleoside guanosine (GUO) has already proven to be effective in reducing reserpine-induced tremulous jaw movements (TJMs) in rodent models, thus becoming a promising antiparkinsonian drug. Here, we aimed at revealing the mechanism behind GUO antiparkinsonian efficacy by assessing the role of adenosine A₁ and A_2A receptors (A₁R and A_2AR) on GUO-mediated anti-tremor effects in the reserpinized mouse model of PD. Reserpinized mice showed elevated reactive oxygen species (ROS) production and cellular membrane damage in striatal slices assessed ex vivo and GUO treatment reversed ROS production. Interestingly, while the simultaneous administration of sub-effective doses of GUO (5 mg/kg) and SCH58261 (0.01 mg/kg), an A_2AR antagonist, precluded reserpine-induced TJMs, these were ineffective on reverting ROS production in ex vivo experiments. Importantly, GUO was able to reduce TJM and ROS production in reserpinized mouse lacking the A_2AR, thus suggesting an A_2AR-independent mechanism of GUO-mediated effects. Conversely, the administration of DPCPX (0.75 mg/kg), an A₁R antagonist, completely abolished both GUO-mediated anti-tremor effects and blockade of ROS production. Overall, these results indicated that GUO anti-tremor and antioxidant effects in reserpinized mice were A₁R dependent but A_2AR independent, thus suggesting a differential participation of adenosine receptors in GUO-mediated effects.

Controlled fabrication of gold nanobipyramids/polypyrrole for shell-isolated nanoparticle-enhanced Raman spectroscopy to detect γ-aminobutyric acid

Shell-isolated nanoparticle-enhanced Raman Spectroscopy (SHINERS) has been a non-destructive, highly sensitive, specific and powerful sensing method. Detection of γ-aminobutyric acid (GABA) and glutamate, main neurotransmitters in the human brain, is important to diagnosis the neurological disorder. The purpose of this study is preparing a simple, rapid and inexpensive fabrication of Au nanobipyramids/polymer core/shell as a SHINERS-based biosensor to detect different neurotransmitters such as GABA and glutamate with high sensitivity and specificity. Au nanobipyramids/polymer core/shell was fabricated by using two steps process. In the first Au nanobipyramids with longitude and latitude axial of about 100 nm and 10 nm, respectively, was prepared based on the chemical reduction of Au ions by using sodium borohydride as a reducing agent. Then a thin layer of polypyrrole was used for decorating the Au nanobipyramids by using direct polymerization in the presence of Au nanobipyramids. The sensor composed Au nanobipyramids with a thin layer of polypyrrole that could measure GABA within a wide range of concentrations in the presence of human serum. And this sensor was used for direct monitoring of GABA and glutamate. The proposed biosensor can be applied to monitor the level of neurotransmitters accurately for the diagnosis of various neurological disorders with optical signal enhancement.

Pharmacological and physiological characterization of the tremulous jaw movement model of parkinsonian tremor: potential insights into the pathophysiology of tremor

Tremor is a cardinal symptom of parkinsonism, occurring early on in the disease course and affecting more than 70% of patients. Parkinsonian resting tremor occurs in a frequency range of 3-7 Hz and can be resistant to available pharmacotherapy. Despite its prevalence, and the significant decrease in quality of life associated with it, the pathophysiology of parkinsonian tremor is poorly understood. The tremulous jaw movement (TJM) model is an extensively validated rodent model of tremor. TJMs are induced by conditions that also lead to parkinsonism in humans (i.e., striatal DA depletion, DA antagonism, and cholinomimetic activity) and reversed by several antiparkinsonian drugs (i.e., DA precursors, DA agonists, anticholinergics, and adenosine A(2A) antagonists). TJMs occur in the same 3-7 Hz frequency range seen in parkinsonian resting tremor, a range distinct from that of dyskinesia (1-2 Hz), and postural tremor (8-14 Hz). Overall, these drug-induced TJMs share many characteristics with human parkinsonian tremor, but do not closely resemble tardive dyskinesia. The current review discusses recent advances in the validation of the TJM model, and illustrates how this model is being used to develop novel therapeutic strategies, both surgical and pharmacological, for the treatment of parkinsonian resting tremor.

Combined extrinsic and intrinsic manipulations exert complementary neuronal enrichment in embryonic rat neural precursor cultures: an in vitro and in vivo analysis

Numerous central nervous system (CNS) disorders share a common pathology in dysregulation of gamma-aminobutyric acid (GABA) inhibitory signaling. Transplantation of GABA-releasing cells at the site of disinhibition holds promise for alleviating disease symptoms with fewer side effects than traditional drug therapies. We manipulated fibroblast growth factor (FGF)-2 deprivation and mammalian achaete-scute homolog (MASH)1 transcription factor levels in an attempt to amplify the default GABAergic neuronal fate in cultured rat embryonic neural precursor cells (NPCs) for use in transplantation studies. Naïve and MASH1 lentivirus-transduced NPCs were maintained in FGF-2 or deprived of FGF-2 for varying lengths of time. Immunostaining and quantitative analysis showed that GABA- and beta-III-tubulin-immunoreactive cells generally decreased through successive passages, suggesting a loss of neurogenic potential in rat neurospheres expanded in vitro. However, FGF-2 deprivation resulted in a small, but significantly increased population of GABAergic cells derived from passaged neurospheres. In contrast to naïve and GFP lentivirus-transduced clones, MASH1 transduction resulted in increased bromodeoxyuridine (BrdU) incorporation and clonal colony size. Western blotting showed that MASH1 overexpression and FGF-2 deprivation additively increased beta-III-tubulin and decreased cyclic nucleotide phosphodiesterase (CNPase) expression, whereas FGF-2 deprivation alone attenuated glial fibrillary acidic protein (GFAP) expression. These results suggest that low FGF-2 signaling and MASH1 activity can operate in concert to enrich NPC cultures for a GABA neuronal phenotype. When transplanted into the adult rat spinal cord, this combination also yielded GABAergic neurons. These findings indicate that, even for successful utilization of the default GABAergic neuronal precursor fate, a combination of both extrinsic and intrinsic manipulations will likely be necessary to realize the full potential of NSC grafts in restoring function.

Effects of the adenosine A 2A antagonist KW 6002 (istradefylline) on pimozide-induced oral tremor and striatal c-Fos expression: comparisons with the muscarinic antagonist tropicamide

Typical antipsychotic drugs, including haloperidol and pimozide, have been shown to produce parkinsonian motor effects such as akinesia and tremor. Furthermore, there is an antagonistic interaction between adenosine A(2A) and dopamine D(2) receptors in the basal ganglia, which is important for motor functions related to the production of parkinsonian symptoms. Several experiments were conducted to assess the effects of the selective adenosine A(2A) antagonist KW 6002 on both the motor and cellular effects of subchronic administration of pimozide. The motor test employed was tremulous jaw movements, which is used as a model of parkinsonian tremor. In addition, c-Fos expression in the ventrolateral neostriatum, which is the striatal area most associated with tremulous jaw movements, was used as a marker of striatal cell activity in animals that were tested in the behavioral experiments. Repeated administration of 1.0 mg/kg pimozide induced tremulous jaw movements and increased ventrolateral striatal c-Fos expression, while administration of 20.0 mg/kg of the atypical antipsychotic quetiapine did not. The tremulous jaw movements induced by pimozide were significantly reduced by co-administration of either the adenosine A(2A) antagonist KW 6002 or the muscarinic antagonist tropicamide. Pimozide-induced increases in ventrolateral striatal c-Fos expression were reduced by a behaviorally effective dose of KW 6002, but c-Fos expression in pimozide-treated rats was actually increased by tropicamide. These results indicate that two different drug manipulations that act to reduce tremulous jaw movements can have different effects on DA antagonist-induced c-Fos expression, suggesting that adenosine A(2A) antagonism and muscarinic receptor antagonism exert their motor effects by acting on different striatal circuits.

Transplantation of GABA-producing cells for seizure control in models of temporal lobe epilepsy

A high percentage of patients with temporal lobe epilepsy (TLE) are refractory to conventional pharmacotherapy. The progressive neurodegenerative processes associated with a lifetime of uncontrolled seizures mandate the development of alternative approaches to treat this disease. Transplantation of inhibitory cells has been suggested as a potential therapeutic strategy to achieve seizure suppression in humans with intractable TLE. Preclinical investigations over 20 years have demonstrated that multiple cell types from several sources can produce anticonvulsant, and antiepileptogenic, effects in animal models of TLE. Transplanting GABA-producing cells, in particular, has been shown to reduce seizures in several well-established models. This review addresses experimentation using different sources of transplantable GABAergic cells, highlighting progress with fetal tissue, neural cell lines, and stem cells. Regardless of the source of the GABAergic cells used in seizure studies, common challenges have emerged. Several variables influence the anticonvulsant potential of GABA-producing cells. For example, tissue availability, graft survival, immunogenicity, tumorigenicity, and varying levels of cell migration, differentiation, and integration into functional circuits and the microenvironment provided by sclerotic tissue all contribute to the efficacy of transplanted cells. The challenge of understanding how all of these variables work in concert, in a disease process that has no well-established etiology, suggests that there is still much basic research to be done before rational cell-based therapies can be developed for TLE.

Improved high-performance liquid chromatographic method for GABA and glutamate determination in regions of the rodent brain

A C18 reversed-phase column and isocratic fluorescence HPLC method for the simultaneous detection of glutamate and gamma-aminobutyric acid (GABA) is described. In this article a fast and more efficient method for the extraction of these neurotransmitters in rat brain tissue is also presented. The supernatant was derivatized with o-phthalaldehyde (OPA) and analyzed by HPLC with fluorescence detection. Intraday reproducibility was 97.0% and 96.7% and interday reproducibility was 97.1% and 93.7% for GABA and glutamate, respectively. Recovery assays indicate that the accuracy of the method for GABA is 99.6+/-2.3% and for glutamate is 101.9+/-1.8%. In addition, the time consumed to run a sample is lower than that described by other authors. Mean elution time was 3.10 min and 8.22 min for glutamate and GABA, respectively. Thus, in a total runtime of less than 9 min both neurotransmitters were detected. Moreover, when compared to the current methods, the extraction solution used here allowed a high drawing out of the neurotransmitters, glutamate and GABA, from the hippocampus, thalamus and prefrontal cortex of the rat brain.

The muscarinic receptor antagonist tropicamide suppresses tremulous jaw movements in a rodent model of parkinsonian tremor: possible role of M4 receptors

RATIONALE

Nonselective muscarinic acetylcholine antagonists have been used for several years as antiparkinsonian drugs. However, there are at least five subtypes of muscarinic receptor (M1-5). Neostriatal M4 receptors have been implicated in aspects of motor function, and it has been suggested that M4 antagonists could be used as treatments for parkinsonism.

OBJECTIVE

Currently, there is a lack of highly selective M4 antagonists that readily penetrate the blood brain barrier. Thus, the present studies focused upon the effects of tropicamide, a muscarinic acetylcholine receptor antagonist with moderate binding selectivity for the M4 receptor subtype.

MATERIALS AND METHODS

Tremulous jaw movements were used as a model of parkinsonian tremor in these studies, and the effects of tropicamide were compared with those of the nonselective muscarinic antagonist atropine.

RESULTS

Tropicamide suppressed the tremulous jaw movements induced by the muscarinic agonist pilocarpine and the dopamine antagonist pimozide. Analysis of the dose-response curves indicated that tropicamide showed approximately the same potency as atropine for suppression of pilocarpine-induced jaw movements but was more potent than atropine on the suppression of pimozide-induced jaw movements. In contrast, atropine was more potent than tropicamide in terms of impairing performance on visual stimulus detection and delayed nonmatch-to-position tasks.

CONCLUSIONS

These studies demonstrate that tropicamide, which currently is used clinically for ophthalmic purposes, can exert actions that are consistent with antiparkinsonian effects. Moreover, the different pattern of effects shown by tropicamide compared to those of atropine on motor vs cognitive tasks could be due to the modest M4 selectivity shown by tropicamide.

GABAergic circuits in the basal ganglia and movement disorders

GABA is the major inhibitory neurotransmitter in the basal ganglia, and GABAergic pathways dominate information processing in most areas of these structures. It is therefore not surprising that abnormalities of GABAergic transmission are key elements in pathophysiologic models of movement disorders involving the basal ganglia. These include hypokinetic diseases such as Parkinson's disease, and hyperkinetic diseases, such as Huntington's disease or hemiballism. In this chapter, we will briefly review the major anatomic features of the GABAergic pathways in the basal ganglia, and then describe in greater detail the changes of GABAergic transmission, which are known to occur in movement disorders.

Injections of the selective adenosine A2A antagonist MSX-3 into the nucleus accumbens core attenuate the locomotor suppression induced by haloperidol in rats

There is considerable evidence of interactions between adenosine A2A receptors and dopamine D2 receptors in striatal areas, and antagonists of the A2A receptor have been shown to reverse the motor effects of DA antagonists in animal models. The D2 antagonist haloperidol produces parkinsonism in humans, and also induces motor effects in rats, such as suppression of locomotion. The present experiments were conducted to study the ability of the adenosine A2A antagonist MSX-3 to reverse the locomotor effects of acute or subchronic administration of haloperidol in rats. Systemic (i.p.) injections of MSX-3 (2.5-10.0 mg/kg) were capable of attenuating the suppression of locomotion induced by either acute or repeated (i.e., 14 day) administration of 0.5 mg/kg haloperidol. Bilateral infusions of MSX-3 directly into the nucleus accumbens core (2.5 microg or 5.0 microg in 0.5 microl per side) produced a dose-related increase in locomotor activity in rats treated with 0.5 mg/kg haloperidol either acutely or repeatedly. There were no overall significant effects of MSX-3 infused directly into the dorsomedial nucleus accumbens shell or the ventrolateral neostriatum. These results indicate that antagonism of adenosine A2A receptors can attenuate the locomotor suppression produced by DA antagonism, and that this effect may be at least partially mediated by A2A receptors in the nucleus accumbens core. These studies suggest that adenosine and dopamine systems interact to modulate the locomotor and behavioral activation functions of nucleus accumbens core.

Motor stimulant effects of ethanol injected into the substantia nigra pars reticulata: importance of catalase-mediated metabolism and the role of acetaldehyde

A series of experiments was conducted to investigate the locomotor effects of local injections of ethanol and the ethanol metabolite, acetaldehyde, into substantia nigra pars reticulata (SNr). Infusions of ethanol into SNr resulted in a dose-related increase in locomotor activity, with maximal effects at a dose of 1.4 micromol. Ethanol injected into a control site dorsal to substantia nigra failed to stimulate locomotion, and another inactive site was identified in brainstem areas posterior to substantia nigra. The locomotor effects of intranigral ethanol (1.4 micromol) were reduced by coadministration of 10 mg/kg sodium azide, a catalase inhibitor that acts to reduce the metabolism of ethanol into acetaldehyde in the brain. SNr infusions of acetaldehyde, which is the first metabolite of ethanol, also increased locomotion. Taken together, these results indicate that SNr is one of the sites at which ethanol and acetaldehyde may be acting to induce locomotor activity. These results are consistent with the hypothesis that acetaldehyde is a centrally active metabolite of ethanol, and provide further support for the idea that catalase activity is a critical step in the regulation of ethanol-induced motor activity. These studies have implications for understanding the brain mechanisms involved in mediating the ascending limb of the biphasic dose-response curve for the effect of ethanol on locomotor activity.

Effects of baclofen on reserpine-induced vacuous chewing movements in mice

We have described that GABA mimetic drugs present the ability to inhibit the expression of reserpine-induced oral movements. In this respect, oral movements is associated with important neuropathologies. This study investigates the effects of an acute or a repeated treatment of different doses of the GABA(B) agonist baclofen, as well as withdrawal from these treatments, on the development and/or expression of reserpine-induced vacuous chewing movements (VCM). Male mice received two injections of vehicle or of 1mg/kg reserpine separated by 48 h. In the first experiment, 24h later, animals were acutely treated with vehicle or baclofen (1, 2 or 4 mg/kg). In the second experiment, animals were treated with vehicle or baclofen (1 or 4 mg/kg) for four consecutive days receiving a concomitant injection of 1mg/kg reserpine (or vehicle) on Days 2 and 4. Twenty-four hours later, animals received vehicle or baclofen. Thirty minutes after the last injection, they were observed for quantification of VCM and open-field general activity. The acute administration of all the doses of baclofen abolished the manifestation of reserpine-induced VCM. Repeated treatment with 1mg/kg baclofen induced tolerance to the ability of an acute injection of this dose to reduce VCM. Treatment with baclofen (4 mg/kg) did not modify spontaneous VCM. Acute administration of the highest dose induced a decrease in general motor activity and a potentiation of the reserpine-induced decrease in general activity. These results reinforce the involvement of GABAergic hypofunction in the expression of oral movements and suggest that a repeated treatment with baclofen induces compensatory changes in GABAergic transmission that can attenuate its acute property to decrease VCM.

The GABA uptake inhibitor beta-alanine reduces pilocarpine-induced tremor and increases extracellular GABA in substantia nigra pars reticulata as measured by microdialysis

Substantia nigra pars reticulata (SNr) is a major output nucleus of the basal ganglia that receives GABAergic projections from neostriatum and globus pallidus. Previous research has shown that local pharmacological manipulations of GABA in SNr can influence tremulous jaw movements in rats. Tremulous jaw movements are defined as rapid vertical deflections of the lower jaw that resemble chewing but are not directed at a particular stimulus, and evidence indicates that these movements share many characteristics with parkinsonian tremor in humans. In order to investigate the role of GABA in motor functions related to tremor, the present study tested the GABA uptake blocker beta-alanine for its ability to reduce pilocarpine-induced tremulous jaw movements. In a parallel experiment, the effect of an active dose of beta-alanine on dialysate levels of GABA in SNr was assessed using microdialysis methods. GABA levels in dialysis samples were measured using high performance liquid chromatography with electrochemical detection. beta-Alanine (250-500 mg/kg) significantly reduced tremulous jaw movements induced by pilocarpine (4.0 mg/kg). Moreover, systemic administration of beta-alanine at a dose that reduced tremulous jaw movements (500 mg/kg) resulted in a substantial increase in extracellular levels of GABA in SNr compared to the pre-injection baseline. Thus, the present results are consistent with the hypothesis that GABAergic tone in SNr plays a role in the regulation of tremulous jaw movements. This research may lead to a better understanding of how parkinsonian symptoms are modulated by SNr GABA mechanisms.

Effect of 17-beta-estradiol on dopamine, serotonine and GABA striatal levels in 6-hydroxydopamine-treated rats

Intrastriatal injection (16microg) of the neurotoxic dopaminergic agent 6-hydroxydopamine (6-OHDA) in ovariectomized rats caused important reductions in striatal dopamine (DA) and serotonin (5-HT) levels and an increase in GABA content. Treatment of ovariectomized rats with estradiol (5 mg 17-beta-estradiol administered by a subcutaneous cannula) before 6-OHDA injection maintained the control levels of these neurotransmitters. The administration of estradiol after 6-OHDA injection did not lead to their recovery. These findings suggest that estradiol acts as a neuroprotectant--but not as a neuroreparatory agent--and that it might be able to attenuate striatal dopaminergic neuron degeneration caused by neurotoxic agents.

The adenosine A2A antagonist KF17837 reverses the locomotor suppression and tremulous jaw movements induced by haloperidol in rats: possible relevance to parkinsonism

Recent evidence indicates that adenosine A2A receptors modulate the activity of striatal neurons, and that antagonists of this receptor may have actions in various animal models related to motor function. Four experiments were conducted to study the effects of systemic injections of the adenosine A2A antagonist KF17837 on the behavioral effects produced by repeated administration of the dopamine (DA) antagonist haloperidol. In the first two experiments, it was shown that repeated 0.5 mg/kg haloperidol severely suppressed open-field locomotor activity, and that KF17837 (0.0-20.0 mg/kg) did not significantly increase open-field locomotor activity. The third experiment demonstrated that injections of KF17837 (0.0-20.0 mg/kg) completely reversed the suppression of locomotion induced by haloperidol, and also increased rearing behavior in haloperidol-treated rats. Previous research has reported that haloperidol induces tremulous jaw movements that have many of the characteristics of parkinsonian tremor. The fourth experiment demonstrated that i.p. injections of KF17837 (0.0-20.0 mg/kg) also suppressed haloperidol-induced tremulous jaw movements. Taken together, the results of these experiments indicate that adenosine A2A antagonism can reverse the locomotor suppression and tremulous movements induced by DA antagonism. This profile of activity is consistent with the hypothesis that antagonism of adenosine A2A receptors can result in an antiparkinsonian effect in animal models.