Michiko Kobayashi

Further evidence for the decay K+ ---> pi+ neutrino anti-neutrino

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Serine 129 Phosphorylation of α-Synuclein Induces Unfolded Protein Response-mediated Cell Death

α-Synuclein is a major protein component deposited in Lewy bodies and Lewy neurites that is extensively phosphorylated at Ser129, although its role in neuronal degeneration is still elusive. In this study, several apoptotic pathways were examined in α-synuclein-overexpressing SH-SY5Y cells. Following the treatment with rotenone, a mitochondrial complex I inhibitor, wild type α-synuclein-overexpressing cells demonstrated intracellular aggregations, which shared a number of features with Lewy bodies, although cells overexpressing the S129A mutant, in which phosphorylation at Ser129 was blocked, showed few aggregations. In wild typeα-synuclein cells treated with rotenone, the proportion of phosphorylated α-synuclein was about 1.6 times higher than that of untreated cells. Moreover, induction of unfolded protein response (UPR) markers was evident several hours before the induction of mitochondrial disruption and caspase-3 activation. Eukaryotic initiation factor 2α, a member of the PERK pathway family, was remarkably activated at early phases. On the other hand, the S129A mutant failed to activate UPR. Casein kinase 2 inhibitor, which decreased α-synuclein phosphorylation, also reduced UPR activation. The α-synuclein aggregations were colocalized with a marker for the endoplasmic reticulum-Golgi intermediate compartment. Taken together, it seems plausible that α-synuclein toxicity is dependent on the phosphorylation at Ser129 that induces the UPRs, possibly triggered by the disturbed endoplasmic reticulum-Golgi trafficking.

The AAA-ATPase VPS4 Regulates Extracellular Secretion and Lysosomal Targeting of α-Synuclein

Many neurodegenerative diseases share a common pathological feature: the deposition of amyloid-like fibrils composed of misfolded proteins. Emerging evidence suggests that these proteins may spread from cell-to-cell and encourage the propagation of neurodegeneration in a prion-like manner. Here, we demonstrated that α-synuclein (αSYN), a principal culprit for Lewy pathology in Parkinsons disease (PD), was present in endosomal compartments and detectably secreted into the extracellular milieu. Unlike prion protein, extracellular αSYN was mainly recovered in the supernatant fraction rather than in exosome-containing pellets from the neuronal culture medium and cerebrospinal fluid. Surprisingly, impaired biogenesis of multivesicular body (MVB), an organelle from which exosomes are derived, by dominant-negative mutant vacuolar protein sorting 4 (VPS4) not only interfered with lysosomal targeting of αSYN but facilitated αSYN secretion. The hypersecretion of αSYN in VPS4-defective cells was efficiently restored by the functional disruption of recycling endosome regulator Rab11a. Furthermore, both brainstem and cortical Lewy bodies in PD were found to be immunoreactive for VPS4. Thus, VPS4, a master regulator of MVB sorting, may serve as a determinant of lysosomal targeting or extracellular secretion of αSYN and thereby contribute to the intercellular propagation of Lewy pathology in PD.

In vivo visualization of α-synuclein deposition by carbon-11-labelled 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy]benzoxazole positron emission tomography in multiple system atrophy

The histopathological hallmark of multiple system atrophy is the appearance of intracellular inclusion bodies, named glial cytoplasmic inclusions, which are mainly composed of alpha-synuclein fibrils. In vivo visualization of alpha-synuclein deposition should be used for the diagnosis and assessment of therapy and severity of pathological progression in multiple system atrophy. Because 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy] benzoxazole could stain alpha-synuclein-containing glial cytoplasmic inclusions in post-mortem brains, we compared the carbon-11-labelled 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy] benzoxazole positron emission tomography findings of eight multiple system atrophy cases to those of age-matched normal controls. The positron emission tomography data demonstrated high distribution volumes in the subcortical white matter (uncorrected P < 0.001), putamen and posterior cingulate cortex (uncorrected P < 0.005), globus pallidus, primary motor cortex and anterior cingulate cortex (uncorrected P < 0.01), and substantia nigra (uncorrected P < 0.05) in multiple system atrophy cases compared to the normal controls. They were coincident with glial cytoplasmic inclusion-rich brain areas in multiple system atrophy and thus, carbon-11-labelled 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy] benzoxazole positron emission tomography is a promising surrogate marker for monitoring intracellular alpha-synuclein deposition in living brains.

Role of TPPP/p25 on α-synuclein-mediated oligodendroglial degeneration and the protective effect of SIRT2 inhibition in a cellular model of multiple system atrophy ☆

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder presenting variable combinations of parkinsonism, cerebellar ataxia, corticospinal and autonomic dysfunction. Alpha-synuclein (α-SYN)-immunopositive glial cytoplasmic inclusions (GCIs) represent the neuropathological hallmark of MSA, and tubulin polymerization promoting protein (TPPP)/p25 in oligodendroglia has been known as a potent stimulator of α-SYN aggregation. To gain insight into the molecular pathomechanisms of GCI formation and subsequent oligodendroglial degeneration, we ectopically expressed α-SYN and TPPP in HEK293T and oligodendroglial KG1C cell lines. Here we showed that TPPP specifically accelerated α-SYN oligomer formation and co-immunoprecipitation analysis revealed the specific interaction of TPPP and α-SYN. Moreover, phosphorylation of α-SYN at Ser-129 facilitated the TPPP-mediated α-SYN oligomerization. TPPP facilitated α-SYN-positive cytoplasmic perinuclear inclusions mimicking GCI in both cell lines; however, apoptotic cell death was only observed in KG1C cells. This apoptotic cell death was partly rescued by sirtuin 2 (SIRT2) inhibition. Together, our results provide further insight into the molecular pathogenesis of MSA and potential therapeutic approaches.

In vivo visualization of tau deposits in corticobasal syndrome by 18F-THK5351 PET

Objective: To determine whether 18F-THK5351 PET can be used to visualize tau deposits in brain lesions in live patients with corticobasal syndrome (CBS). Methods: We evaluated the in vitro binding of 3H-THK5351 in postmortem brain tissues from a patient with corticobasal degeneration (CBD). In clinical PET studies, 18F-THK5351 retention in 5 patients with CBS was compared to that in 8 age-matched normal controls and 8 patients with Alzheimer disease (AD). Results: 3H-THK5351 was able to bind to tau deposits in the postmortem brain with CBD. In clinical PET studies, the 5 patients with CBS showed significantly higher 18F-THK5351 retention in the frontal, parietal, and globus pallidus than the 8 age-matched normal controls and patients with AD. Higher 18F-THK5351 retention was observed contralaterally to the side associated with greater cortical dysfunction and parkinsonism. Conclusions: 18F-THK5351 PET demonstrated high tracer signal in sites susceptible to tau deposition in patients with CBS. 18F-THK5351 should be considered as a promising candidate radiotracer for the in vivo imaging of tau deposits in CBS.

Functional imaging studies of hyposmia in Parkinson's disease

Hyposmia in Parkinsons disease (PD) was evaluated by using neuroimaging techniques. It is well known that olfactory impairments are one of the cardinal non-motor symptoms in PD. However, all smell tests used in previous studies depend on subjective answers by examinees and on sniffing of odorants, the latter of which may be impaired in PD as a consequence of motor impairments. We developed an fMRI system, which can visualize brain activation by olfactory stimuli during natural breathing. Although 7 age-matched controls demonstrated significant activations in various brain areas including precentral gyrus (BA6/6) and middle temporal gyrus (BA19/39) by the odorant stimuli, 9 patients with PD showed little activations by the same stimuli. These data suggest that the olfactory dysfunction in PD is not a simple reflection of impaired sniffing. Recent epidemiological studies demonstrate that the olfactory impairments may precede the onset of motor symptoms. Moreover, several pathological studies suggest that amygdala is one of the most frequently affected regions and is closely related to hyposmia in PD. Further brain imaging studies of hyposmia will shed light on the early pathological changes in PD.

Bilateral frontal cortex encephalitis and paraparesis in a patient with anti-MOG antibodies.

Encephalitis seldom causes paraparesis as the initial symptom. Here, we report a case of steroid-responsive bilateral frontal cortical encephalitis involving leg motor areas in a patient who presented with paraparesis on admission. Interestingly, the initial paraparesis evolved into an acute disseminated encephalomyelitis (ADEM)-like illness and optic neuritis, and the patient was found to be positive for anti-myelin oligodendrocyte glycoprotein (MOG) antibodies. A 46-year-old man experienced transient dizziness in early September 2008. Brain MRI retrospectively showed a slight fluid attenuation inversion recovery (FLAIR) high-intensity lesion involving the left frontal cortex (figure 1). One week later, the patient experienced a focal motor seizure in the right leg that subsequently generalised. Thereafter, he gradually developed headache and paraparesis over the course of a week. On admission, he presented with paraparesis without other neurological deficits, but the spinal MRI was normal. An electroencephalogram revealed that there were no epileptic discharges. A cerebrospinal fluid (CSF) examination revealed elevated leucocytes (56 /µL; 93% mononuclear cells, 3% polymorphonuclear leucocytes) and normal protein (36 mg/dL) and glucose (59 mg/dL) levels. The myelin basic protein (MBP) and glial fibrillary acidic protein levels in the CSF were not elevated. Cell-based assays for anti-N-methyl-D-aspartate receptor (NMDAR) antibodies, anti-voltage-gated potassium channel (VGKC) antibodies, anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antibodies and anti-γ-aminobutyric acid-B receptor (GABA(B)R) antibodies in the CSF were negative. Blood and CSF examinations for infectious central nervous system (CNS) CNS diseases, collagen diseases, vasculitis, Behcet disease, sarcoidosis, lymphoma, paraneoplastic syndrome, vitamin B deficiency and Hashimoto encephalopathy were unremarkable. Figure 1 Upper panel: axial fluid attenuation inversion recovery (FLAIR) images (1.5 T; TR 6000 ms, TE 105 ms). (A) Brain MRI at …

Hypometabolism in the supplementary and anterior cingulate cortices is related to dysphagia in Parkinson's disease: a cross-sectional and 3-year longitudinal cohort study

Objective Dysphagia is one of the cardinal symptoms of Parkinson’s disease (PD). It is closely related to the quality of life and longevity of PD patients. The aim of the study is to clarify the pathophysiological mechanisms responsible for dysphagia in PD. Design A cross-sectional and longitudinal comparative study. Setting Tohoku University Hospital. Participants Eight patients with dysphagia, 15 patients without dysphagia and 10 normal control subjects. Main outcome measures The time needed for swallowing initiation and changes in brain glucose metabolism at baseline and after a 3-year follow-up period. Results The time needed for swallowing initiation was significantly longer in the patients with dysphagia compared with the patients without dysphagia at baseline and after the 3-year follow-up period (p<0.05). The patients with dysphagia exhibited hypometabolism in the supplementary motor area (SMA) and the anterior cingulate cortex (ACC) compared with the 10 normal control subjects at baseline (uncorrected p<0.001). After the 3-year follow-up period, the number of brain areas showing hypometabolism increased, involving not only the SMA and the ACC but also the bilateral medial frontal lobes, middle cingulate cortex, thalamus and right superior, middle, inferior and orbital frontal gyri (uncorrected p<0.001). In contrast, the patients without dysphagia showed virtually no regional hypometabolism at baseline (uncorrected p<0.001) and only a small degree of hypometabolism in the SMA and ACC after the 3-year follow-up period (uncorrected p<0.001). Conclusions These results suggest that dysphagia in PD patients is mainly related to a difficulty in swallowing initiation that is based on a combination of poor movement planning due to SMA dysfunction and impaired cognitive processing due to ACC dysfunction.

Measurement of structure-dependent K+ --> m(+)nu(m)gamma decay

We report the first measurement of a structure dependent component in the decay K^+ ->mu^+ nu gamma. Using the kinematic region where the muon kinetic energy is greater than 137 MeV and the photon energy is greater than 90 MeV, we find that the absolute value of the sum of the vector and axial-vector form factors is |F_V+F_A| =0.165 \pm 0.007 \pm 0.011. This corresponds to a branching ratio of BR(SD^+) = (1.33 \pm 0.12 \pm 0.18) \times 10^{-5}. We also set the limit -0.04