Akihito Watanabe

1-Methyl-4-phenylpyridinium (MPP+) Decreases Mitochondrial Oxidation-Reduction (REDOX) Activity and Membrane Potential (Δψm) in Rat Striatum

Mitochondrial dysfunction has long been implicated in the death of nigrostriatal dopaminergic neurons in Parkinsons disease (PD) and its experimental models. Here we further analyzed changes in the mitochondrial oxidation-reduction (REDOX) activity and membrane potential (Δψm) of striatal synaptosomes after the infusion of 1-methyl-4-phenylpyridinium (MPP+) into rat striatum. MPP+ (40 nmol) treatment produced decreases in mitochondrial REDOX activity and Δψm at 18 h, as measured by fluorometric analysis with both Alamar blue and JC-1 (5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolyl-carbocyanine iodide) dyes. At this time point, tyrosine hydroxylase (TH) and dopamine transporter (DAT) protein levels were not altered, but both decreased at 7 days after MPP+ (40 nmol) infusion. Both measures of mitochondrial dysfunction induced by MPP+ (40 nmol) at 18 h were attenuated, at least in part, by pretreatment with a selective dopamine uptake inhibitor GBR-12909 (1-(2-(bis(4-fluorophenyl)methoxy)ethyl)-4-(3-phenylpropyl) piperazine). In addition, GBR-12909 partially attenuated MPP+ (40 nmol)-caused a loss of striatal nerve terminal as indicated by decreases in TH and DAT immunoreactivities as well as dopamine and its metabolites levels. The present study indicates that decreases in mitochondrial REDOX activity and Δψm may play a role in MPP+-induced dopaminergic neurotoxicity, and further provides that improvement of mitochondrial dysfunction may be a better way to slow progressive dopaminergic neurodegeneration commonly associated with PD.

Global Trends in Alzheimer Disease Clinical Development: Increasing the Probability of Success

PURPOSE Alzheimer disease (AD) is a growing global health and economic issue as elderly populations increase dramatically across the world. Despite the many clinical trials conducted, currently no approved disease-modifying treatment exists. In this commentary, the present status of AD drug development and the grounds for collaborations between government, academia, and industry to accelerate the development of disease-modifying AD therapies are discussed. METHODS Official government documents, literature, and news releases were surveyed by MEDLINE and website research. FINDINGS Currently approved anti-AD drugs provide only short-lived symptomatic improvements, which have no effect on the underlying pathogenic mechanisms or progression of the disease. The failure to approve a disease-modifying drug for AD may be because the progression of AD in the patient populations enrolled in clinical studies was too advanced for drugs to demonstrate cognitive and functional improvements. The US Food and Drug Administration and the European Medicines Agency recently published draft guidance for industry which discusses approaches for conducting clinical studies with patients in early AD stages. For successful clinical trials in early-stage AD, however, it will be necessary to identify biomarkers highly correlated with the clinical onset and the longitudinal progress of AD. In addition, because of the high cost and length of clinical AD studies, support in the form of global initiatives and collaborations between government, industry, and academia is needed. IMPLICATIONS In response to this situation, national guidance and international collaborations have been established. Global initiatives are focusing on 2025 as a goal to provide new treatment options, and early signs of success in biomarker and drug development are already emerging.

Olfactory impairment and Parkinson's disease-like symptoms observed in the common marmoset following administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

OBJECTIVE Although olfactory disturbance appears to occur in the early stages of Parkinsons disease (PD) in humans, little is known about its mechanism. The aim of this study was to make a PD model using injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the common marmoset and to discover the mechanism of olfactory disturbance in this animal. MATERIAL AND METHODS Olfactory disturbance induced by MPTP in the common marmoset was observed by behavioral, biochemical and immunohistochemical means. RESULTS Administration of MPTP caused common marmosets to enter an akinetic state within a few days and to show signs of impaired olfactory function. Biochemical study showed a decrease in dopamine levels, especially in tissue samples from the caudate nucleus and putamen. Immunohistochemical analysis revealed a lack of tyrosine hydroxylase immunoreactivity, not only in the substantia nigra, caudate nucleus and putamen but also in the olfactory tubercle. CONCLUSION These results demonstrate that MPTP causes both PD-like symptoms and olfactory disturbance in the common marmoset. The olfactory disturbance observed in these animals may be due to the lack of dopamine in the olfactory tubercle.

MK-801-induced deficits in social recognition in rats: reversal by aripiprazole, but not olanzapine, risperidone, or cannabidiol.

Deficiencies in social activities are hallmarks of numerous brain disorders. With respect to schizophrenia, social withdrawal belongs to the category of negative symptoms and is associated with deficits in the cognitive domain. Here, we used the N-methyl-D-aspartate receptor antagonist dizocilpine (MK-801) for induction of social withdrawal in rats and assessed the efficacy of several atypical antipsychotics with different pharmacological profiles as putative treatment. In addition, we reasoned that the marijuana constituent cannabidiol (CBD) may provide benefit or could be proposed as an adjunct treatment in combination with antipsychotics. Hooded Lister rats were tested in the three-chamber version for social interaction, with an initial novelty phase, followed after 3 min by a short-term recognition memory phase. No drug treatment affected sociability. However, distinct effects on social recognition were revealed. MK-801 reduced social recognition memory at all doses (>0.03 mg/kg). Predosing with aripiprazole dose-dependently (2 or 10 mg/kg) prevented the memory decline, but doses of 0.1 mg/kg risperidone or 1 mg/kg olanzapine did not. Intriguingly, CBD impaired social recognition memory (12 and 30 mg/kg) but did not rescue the MK-801-induced deficits. When CBD was combined with protective doses of aripiprazole (CBD–aripiprazole at 12 : 1 or 5 : 2 mg/kg) the benefit of the antipsychotic was lost. At the same time, activity-related changes in behaviour were excluded as underlying reasons for these pharmacological effects. Collectively, the combined activity of aripiprazole on dopamine D2 and serotonin 5HT1A receptors appears to provide a significant advantage over risperidone and olanzapine with respect to the rescue of cognitive deficits reminiscent of schizophrenia. The differential pharmacological properties of CBD, which are seemingly beneficial in human patients, did not back-translate and rescue the MK-801-induced social memory deficit.

Altered emotional behaviors in the diabetes mellitus OLETF type 1 congenic rat.

GPR10 is a G-protein-coupled receptor expressed in thalamic and hypothalamic brain regions, including the reticular thalamic nucleus (RTN) and periventricular nucleus (Pev), and the endogenous ligand for this receptor, prolactin-releasing peptide (PrRP), has demonstrated regulatory effects on the stress response. We produced a congenic rat by introducing the Dmo1 allele from the OLETF rat which encodes the amino acid sequences of GPR10 with a truncated NH2-terminus, into the Brown-Norway background. Using receptor autoradiography, we determined a lack of specific [125I]PrRP binding in the RTN and Pev of these mutant rats compared to the control rats. Furthermore, intracerebroventricular injection of PrRP did not induce a significant increase of c-fos-like immunoreactivity in the paraventricular nucleus of the mutant rats compared to the control rats. The mutant rats also displayed a less anxious-like phenotype in three behavioral-based models of anxiety-like behavior (open field, elevated plus maze and defensive withdrawal test). These data show the mutant congenic rat, of which GPR10 neither binds nor responds to PrRP, expresses less anxious-like phenotypes. On the basis of these observations, the GPR10 might be a novel target for the developing new drugs against anxiety and/or other stress-related diseases.

Stimulation of the regrowth of MPP+-damaged dopaminergic fibers by the treatment of mesencephalic cultures with basigin

Summary. Basigin (Bsg) is a transmembrane glycoprotein belonging to the immunoglobulin superfamily and widely expressed in the central nervous system. To elucidate functional role of Bsg in the central nervous system, the effects of its glutathione-S-transferase (GST) fusion protein on the number and neurite outgrowth of cultured rat mesencephalic dopaminergic neurons were measured. The fusion protein was not able to promote the survival and neurite outgrowth of tyrosine hydroxylase (TH)-positive neurons under serum-free condition. However, the treatment of 1-methyl-4-phenylpyridinium (MPP+)-exposed cultures with the fusion protein resulted in stimulation of the regrowth of damaged TH-positive fibers. Basic fibroblast growth factor (bFGF) also stimulated the regrowth of neurites in damaged neurons. These results indicate that Bsg may play an important role in the regrowth of damaged dopaminergic fibers.