Biomedical subjects

Takahiro Sasaki

Publications and source records attributed to Takahiro Sasaki.

At least 19 recordsLinked to original sources

PubMed2022

Reversal of cancer gene expression identifies repurposed drugs for diffuse intrinsic pontine glioma.

Diffuse intrinsic pontine glioma (DIPG) is an aggressive incurable brainstem tumor that targets young children. Complete resection is not possible, and chemotherapy and radiotherapy are currently only palliative. This study aimed to identify potential therapeutic agents using a computational pipeline to perform an in silico screen for novel drugs. We then tested the identified drugs against a panel of patient-derived DIPG cell lines. Using a systematic computational approach with publicly available databases of gene signature in DIPG patients and cancer cell lines treated with a library of clinically available drugs, we identified drug hits with the ability to reverse a DIPG gene signature to one that matches normal tissue background. The biological and molecular effects of drug treatment was analyzed by cell viability assay and RNA sequence. In vivo DIPG mouse model survival studies were also conducted. As a result, two of three identified drugs showed potency against the DIPG cell lines Triptolide and mycophenolate mofetil (MMF) demonstrated significant inhibition of cell viability in DIPG cell lines. Guanosine rescued reduced cell viability induced by MMF. In vivo, MMF treatment significantly inhibited tumor growth in subcutaneous xenograft mice models. In conclusion, we identified clinically available drugs with the ability to reverse DIPG gene signatures and anti-DIPG activity in vitro and in vivo. This novel approach can repurpose drugs and significantly decrease the cost and time normally required in drug discovery.

Humans↗

PubMed2006

Alpha-internexin is structurally and functionally associated with the neurofilament triplet proteins in the mature CNS.

Alpha-internexin, a neuronal intermediate filament protein implicated in neurodegenerative disease, coexists with the neurofilament (NF) triplet proteins (NF-L, NF-M, and NF-H) but has an unknown function. The earlier peak expression of alpha-internexin than the triplet during brain development and its ability to form homopolymers, unlike the triplet, which are obligate heteropolymers, have supported a widely held view that alpha-internexin and neurofilament triplet form separate filament systems. Here, we demonstrate, however, that despite a postnatal decline in expression, alpha-internexin is as abundant as the triplet in the adult CNS and exists in a relatively fixed stoichiometry with these subunits. Alpha-internexin exhibits transport and turnover rates identical to those of triplet proteins in optic axons and colocalizes with NF-M on single neurofilaments by immunogold electron microscopy. Alpha-internexin also coassembles with all three neurofilament proteins into a single network of filaments in quadruple-transfected SW13vim(-) cells. Genetically deleting NF-M alone or together with NF-H in mice dramatically reduces alpha-internexin transport and content in axons throughout the CNS. Moreover, deleting alpha-internexin potentiates the effects of NF-M deletion on NF-H and NF-L transport. Finally, overexpressing a NF-H-LacZ fusion protein in mice induces alpha-internexin and neurofilament triplet to aggregate in neuronal perikarya and greatly reduces their transport and content selectively in axons. Our data show that alpha-internexin and the neurofilament proteins are functionally interdependent. The results strongly support the view that alpha-internexin is a fourth subunit of neurofilaments in the adult CNS, providing a basis for its close relationship with neurofilaments in CNS diseases associated with neurofilament accumulation.

Animals↗

PubMed2006

Release of band cells from the bone marrow is impaired by preoperative chemoradiation in patients with esophageal carcinoma: increased risk of postoperative pneumonia.

PURPOSE: To examine the difference in hematological data and postsurgical course after esophagectomy between patients receiving preoperative chemoradiation and patients without preoperative treatment. METHODS: Twenty-two patients with squamous cell carcinoma of the esophagus who underwent esophagectomy during the past 2 years were retrospectively analyzed in the study. Six patients had preoperative chemoradiation (CRT group) and 16 patients had no preoperative treatment (non-CRT group). The hematological data, postoperative course, and surgical complications were compared between the two groups. RESULTS: Patients in the CRT group were given cisplatin and 5-FU (143 and 6,000 mg on average, respectively) plus an average of 35 Gy of radiation. Although the neutrophil count did not show a significant difference between the two groups, the band cell count was lower in the CRT group compared with the non-CRT group on postoperative day 1 (P<0.05). Postoperative pneumonia was detected in three patients (50%) from the CRT group versus none of the non-CRT group. CONCLUSION: Preoperative CRT may be a risk factor for postoperative pneumonia in patients with esophageal carcinoma who undergo esophagectomy. The normal bone marrow response of releasing band cells from the postmitotic marrow pool after surgery could be disturbed by CRT, which might contribute to an increase in later pulmonary complications.

Aged↗

PubMed2006

Co-morbidity of moyamoya disease with Graves' disease. report of three cases and a review of the literature.

Moyamoya disease is a cerebrovascular disorder characterized by bilateral stenosis or occlusion of the terminal portions of the internal carotid arteries accompanied by typical net-like collateral vessels in the basal ganglia. Although the etiology of moyamoya disease remains unknown, hereditary and immunogenic as well as hemodynamic factors have been implicated in the underlying mechanism of moyamoya disease. We report two patients with confirmed moyamoya disease and a patient with probable moyamoya disease complicated with Graves' disease. We reviewed the literature and summarized 23 cases of moyamoya disease or probable moyamoya, coexisting with Graves' disease.

Adolescent↗

PubMed2006

Aggregate formation and phosphorylation of neurofilament-L Pro22 Charcot-Marie-Tooth disease mutants.

Charcot-Marie-Tooth disease (CMT) is the most common inherited peripheral nerve disorder. The causative gene for axonal type CMT2E has been identified as neurofilament light (NF-L) chain. Using cultured cells and in vitro assays, we analyzed the filament formation ability of Pro22 CMT mutant proteins of NF-L, P22S and P22T. NF-L Pro22 mutant proteins formed large aggregates in SW13- cells and cortical neurons and assembled into short twisty threads thinner than 10 nm filaments in vitro. Those threads associated with each other at their ends and entangled into large aggregates, also abnormalities, were detected at steps in oligomer formation. Pro22 mutations abolished Thr21 phosphorylation by cyclin-dependent kinase 5 and external signal regulated kinase, which suppressed filament assembly, but phosphorylation by protein kinase A (PKA) inhibited aggregate formation in vitro and alleviated aggregates in cortical neurons. These results indicate that the Pro22 CMT mutation induces abnormal filament aggregates by disrupting proper oligomer formation and the aggregates are mitigated by phosphorylation with PKA, which makes it a viable target for the development for therapeutics.

Amino Acid Substitution↗

PubMed2005

Nedd9 protein, a Cas-L homologue, is upregulated after transient global ischemia in rats: possible involvement of Nedd9 in the differentiation of neurons after ischemia.

BACKGROUND AND PURPOSE: Some proteins involved in self-repair after stroke in the adult brain are primarily expressed during embryonic development and strongly down-regulated during the early postnatal phase. Neuronal precursor cell-expressed, developmentally down-regulated gene (Nedd) 9 was recognized to be identical to Crk-associated substrate lymphocyte type (Cas-L), a docking protein that associates with a variety of signaling molecules, such as focal adhesion kinase (FAK), proline-rich tyrosine kinase 2 (Pyk2), and Crk. We investigated the involvement of these proteins in the pathophysiology of global cerebral ischemia. METHODS: The mouse Cas-L/Nedd9 cDNAs were cloned. The expression and function of Cas-L/Nedd9 protein in the pathogenesis of global ischemia in rats was investigated by RT-PCR, Western blot analysis, and immunohistochemistry. The neurite outgrowth of the transfectants of Nedd9 deletion mutants in PC-12 cells was also assessed to clarify the function of the Nedd9 protein. RESULTS: Nedd9 was a splicing variant of Cas-L and was selectively induced in neurons of the cerebral cortex and hippocampus 1 to 14 days after the ischemia. Induced Nedd9 protein was tyrosine phosphorylated and was bound to FAK in dendrite and soma of neurons after the ischemia. Finally, it was demonstrated that Nedd9 promoted neurite outgrowth of PC-12 cells. CONCLUSIONS: Our study may support the potential of Nedd9 for participation in the differentiation of neurons after global ischemia in rats.

Adaptor Proteins, Signal Transducing↗

PubMed2005

HTLV-I Tax induces and associates with Crk-associated substrate lymphocyte type (Cas-L).

Crk-associated substrate lymphocyte type (Cas-L) is a docking protein that is heavily tyrosine phosphorylated by the engagement of beta1 integrins in T cells. In the present study, we attempted to evaluate the role of Cas-L in the pathophysiology of adult T-cell leukemia (ATL). Examination of peripheral blood mononuclear cells from ATL patients as well as ATL-derived T cell lines showed an elevation of Cas-L in these cells. We showed that tyrosine phosphorylation as well as expression of Cas-L was markedly elevated through the induction of human T-lymphotropic virus type I (HTLV-I) Tax in JPX-9 cells, with these cells showing marked motile behavior on the ligands for integrins. We next performed yeast two-hybrid screening of cDNA library from an HTLV-I-transformed T cell line, which resulted in the identification of Tax as a putative binding partner for Cas-L. Co-precipitation experiments revealed that the serine-rich region of Cas-L might serve as the binding site with the highest affinity for Tax. Co-localization study showed that Tax and Cas-L partly merged in the cytoplasm. Finally, we showed that exogenous Cas-L inhibited Tax-mediated transactivation of nuclear factor kappaB (NF-kappaB), while Tax-independent activation of NF-kappaB remained intact, hence indicating that Cas-L might specifically regulate Tax-NF-kappaB pathway.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Ordered progress of spermiogenesis to the fertilizable sperm of the medaka fish, Oryzias latipes, in cell culture.

Spermiogenesis is significant for producing sperm with equipment for achieving fertilization. Although multiple events occur in a particular order during spermiogenesis, it is unclear how the timing of those events is controlled. In the present study, we found that primary spermatocytes obtained from the spermatogenic testes of Oryzias latipes synchronously differentiated into sperm without contact with somatic cells in culture. Because those sperm can fertilize with mature eggs (Saiki et al., 1997), any events of spermiogenesis that are essential for achieving fertilization are completed in the in vitro spermiogenesis. In the in vitro spermiogenesis, the protamine gene expression was observed in the early period and mitochondrion localization was established in the same period. Those results suggest that both nuclear remodeling and organelle replacement begin in the early period of spermiogenesis. The cytoplasmic lobe was formed after the mitochondrion localization had been established. In most spermatids differentiated in cell culture, a flagellum began to elongate during the early period and continued to elongate up to 3 days. These results revealed the timings of the spermiogenetic events under the intrinsic control of the cultured spermatids toward the formation of fertilizable sperm in O. latipes.

Animals↗

PubMed2005

Roxithromycin specifically inhibits development of collagen induced arthritis and production of proinflammatory cytokines by human T cells and macrophages.

OBJECTIVE: Roxithromycin (RXM) is a macrolide antibiotic that is effective in treatment of chronic lower respiratory tract diseases including diffuse panbronchiolitis and bronchial asthma. Its mechanism of action apart from its antibacterial action remains unclear. To determine the mechanism of action of RXM, we evaluated the effect of RXM on T cell functions and the inflammatory responses in mice with collagen induced arthritis (CIA). METHODS: T cell proliferation, cytokine production by T cells stimulated through CD28, CD26, or PMA with or without anti-CD3 Mab, cytokine production by macrophages stimulated with lipopolysaccharide, and transendothelial migration of T cells were analyzed in the presence or absence of various concentrations of RXM. We evaluated the effect of RXM treatment in collagen induced arthritis in mice. RESULTS: RXM did not affect the production of Th1-type and Th2-type cytokines, whereas it specifically inhibited production of proinflammatory cytokines such as tumor necrosis factor-a and interleukin 6 (IL-6) by T cells and macrophages. RXM inhibited T cell migration. We found that RXM treatment of mice with CIA reduced the severity of arthritis and serum level of IL-6, as well as leukocyte migration into the affected joints and destruction of bones and cartilage. CONCLUSION: Our findings strongly suggest that RXM may be useful for the therapy of rheumatoid arthritis as well as other inflammatory diseases such as Crohn's disease.

Animals↗

PubMed2004

FK506 abrogates delayed neuronal death via suppression of nitric oxide production in rats.

BACKGROUND AND PURPOSE: The mechanism of the neuroprotective effect of FK506 in relation to nitric oxide (NO) production has not been clarified in vivo. We have investigated the effect of FK506 on ischemia-induced NO production in association with the pathogenesis of delayed neuronal death (DND) in rats. METHODS: In vivo microdialysis was performed in the hippocampus of male Sprague-Dawley rats (250-350 g). Dialysate samples were collected every 3 min. In the ischemia group (n=16), global ischemia was induced for 21 min and reperfusion was achieved. In the FK506 treatment group (n=25), FK506 (1 mg/kg, i.v.) was administered 21 min prior to the onset of global ischemia. Sham operations were done (n=15). The levels of NO(2)(-) in the dialysate samples were determined by the Griess reaction. The animals were decapitated 7 days after ischemia. Coronal brain sections were stained with hematoxylin and eosin. RESULTS: In the ischemia group, the NO(2)(-) level significantly increased during ischemia. In the FK506 treatment group, there was no significant change in the NO(2)(-) level during ischemia. In histological examinations, FK506 treatment showed a neuroprotective effect against DND. CONCLUSIONS: The effect of FK506 inhibiting NO production contributes to the neuro-protective effect of FK506 on DND in the hippocampus.

Analysis of Variance↗

PubMed2003

Planar reflection grating lens for compact spectroscopic imaging system.

A compact spectroscopic imaging device consisting of a planar reflection grating lens, a probe fiber array, and a two-dimensional image sensor was proposed and discussed. Reflected or luminescent lights from a subject are coupled to the probe fibers, guided to fiber output ends, radiated into the air, diffracted by the grating lens with wavelength-dependent angle, and focused onto lines on the image sensor. Two-dimensional intensity distribution on the image sensor can give one-dimensional spectrum distribution along a specified direction. A grating lens was designed with a fiber array and a CCD image sensor for 100-nm wavelength range and 10-mm fiber array width. A spectral resolution of 5 nm and a spatial resolution of 0.25 mm were experimentally confirmed.

Journal Article↗

PubMed2003

[SPECT imaging using [123I]beta-CIT and [123I]IBF in extrapyramidal diseases].

Imaging of dopaminergic function is useful in the investigation of patients with Parkinson disease (iPD) and other extrapyramidal diseases. Using agents that bind to dopamine transporters ([123I]beta-CIT) and receptors ([123I]IBF SPECT), we investigated SPECT in 9 healthy volunteers and 24 patients for dopamine transporters as well as 15 patients for dopamine receptors. In beta-CIT SPECT studies, we examined 17 iPD patients (63.3 +/- 9.9 y/o), 3 multiple system atrophy (MSA) patients (OPCA type) (64.0 +/- 8.0 y/o), 2 vascular parkinsonism (VP) patients (71.0 +/- 0.0 y/o), 1 progressive supranuclear palsy (PSP) patient (69 y/o), 1 cortico-basal degeneration (CBD) patient (50 y/o) and nine healthy controls (39.1 +/- 9.3 y/o). For IBF SPECT studies 11 iPD patients (60.6 +/- 10.9 y/o), 3 MSA patients (2 OPCA type (50.5 +/- 3.5 y/o) and 1 SND type (65 y/o)) and 1 PSP patient (60 y/o) underwent SPECT scans after the injection of [123I]IBF. The specific to nonspecific striatal uptake ratio(St/Oc-1), ratio of putaminal uptake to caudatal uptake (Pu/Ca), and asymmetry indices (AI) were estimated. beta-CIT studies showed St/Oc-1 as follows; iPD: 2.66 +/- 1.09 (n = 17), VP: 5.73 and 7.39, MSA: 1.84 +/- 0.46 (n = 3), PSP: 2.34, CBD: 2.16. In all extrapyramidal diseases except VP, St/Oc-1 ratios were significantly lower than those in normal volunteers (6.46 +/- 1.08) (p < 0.01). Also in early-phase iPD patients (Yahr I-II), St/Oc-1 (3.16 +/- 1.49: n = 4) was significantly lower than those in normal volunteers (p < 0.01). In IBF studies, St/Oc-1 ratios were significantly higher in early-phase (Yahr I-II) iPD patients (1.82 +/- 0.25: n = 5) than those in late-phase (Yahr III-IV) iPD patients (1.38 +/- 0.32: n = 6) (p < 0.05). The Pu/Ca ratios in iPD patients (1.12 +/- 0.13) and MSA (OPCA type) patients (0.95 +/- 0.05) were higher than that in MSA (SND type) patient (0.78) and were lower than that in PSP patient (1.55). In conclusion, beta-CIT-SPECT is useful for the diagnosis of early-phase iPD patients and for differentiating VP from other extrapyramidal diseases. IBF-SPECT is useful for the diagnosis of the severity of iPD and has the possibility for ruling out MSA (SND type) or PSP from iPD. Both tracers are useful for investigating the pathophysiology of patients with iPD and other extrapyramidal diseases.

Aged↗

PubMed2002

Subcellular localization of a promoter and an inhibitor of apoptosis (Smac/DIABLO and XIAP) during brain ischemia/reperfusion.

We explored the expression of Smac/DIABLO, a newly identified mitochondrial apoptogenic molecule, and X-linked inhibitor of apoptosis protein (XIAP) in the brain subjected to ischemia/reperfusion. Transient focal ischemia was produced for 1 hour in mice. We observed only a negligible amount of Smac/DIABLO in both mitochondria and cytosol in the normal state. The mitochondrial expression level of Smac/DIABLO increased after 2-11 h reperfusion. There was increased Smac/DIABLO expression in the cytosol after 5 h reperfusion, implying the translocation of Smac/DIABLO into the cytosol. The subcellular localization of XIAP became more extensive within the cells during reperfusion, as compared with the normal state. Our results imply that Smac/DIABLO and XIAP are implicated in the pathophysiological mechanisms of reperfusion injury.

Animals↗

PubMed2002

In vivo and in vitro phosphorylation at Ser-493 in the glutamate (E)-segment of neurofilament-H subunit by glycogen synthase kinase 3beta.

Neurofilament (NF), a major neuronal intermediate filament, is composed of three subunits, NF-L, NF-M, and NF-H. All three subunits contain a well conserved glutamate (E)-rich region called "E-segment" in the N terminus of the tail region. Although the E-segments of NF-L and NF-M are phosphorylated by casein kinases, it has not been observed in NF-H. Using mass spectrometric analysis, we identified phosphorylation of the E-segment of NF-H, prepared from rat spinal cords, at Ser-493 and Ser-501 in the Ser-Pro sequences. The E-segment kinase was isolated from rat brain extract using column chromatography and identified as glycogen synthase kinase (GSK) 3beta. GSK3beta was shown to phosphorylate at Ser-493 in vitro by phosphopeptide mapping and site-directed mutagenesis, and in vivo in HEK293 cells using the phospho-Ser-493 antibody, but did not phosphorylate Ser-501. GSK3beta preferred Ser-493 to the KSP-repeated sequences for phosphorylation sites in the NF-H tail domain. Moreover, Ser-493 was a better phosphorylation site for GSK3beta than other proline-directed protein kinases, Cdk5/p35 and ERK. GSK3beta in the spinal cord extract was associated with NF cytoskeletons. Taken together, we concluded that Ser-493 in the E-segment of NF-H is phosphorylated by GSK3beta in rat spinal cords.

Amino Acid Sequence↗

PubMed2002

Upregulation of Akt phosphorylation at the early stage of middle cerebral artery occlusion in mice.

Akt is a serine/threonine kinase that is believed to promote cell viability in many different cell types, including neurons. Here, we observed the state of Akt phosphorylation at several time points (1, 3, 6, 12, and 24 h) during permanent occlusion of the middle cerebral artery (MCA) in mice. We detected a transient upregulation of Akt phosphorylation at 1 h of MCA occlusion (MCAO) by Western blot analysis. Double immunostaining revealed that the enhanced phosphorylation of Akt occurred mainly in neurons located in the outer area of the MCA territory (ischemic penumbra). This phenomenon was accompanied by the nuclear translocation of Akt. We confirmed that Akt enzymatic activity is elevated in both the nuclear and cytosolic fractions of brain tissue subjected to 1 h of ischemia. cAMP-response-element-binding protein (CREB), an intranuclear target molecule of Akt, exhibited increased phosphorylation after 1 h of MCAO. In our ischemia model, caspase-3 was activated in the central part of the MCA territory as little as 1 h after MCAO. However, caspase-3 activation was not recognized at this time in the outer area of the MCA territory, where Akt activity was upregulated. These results suggest that prosurvival cell signaling is initiated in an active fashion before cell death pathways are activated in neurons situated in the ischemic penumbra at the early stage of ischemia.

Animals↗

PubMed2002

Distinctive signaling pathways through CD82 and beta1 integrins in human T cells.

CD82, a member of tetraspan family (tetraspanin), is a multifunctional molecule that is involved in cell activation, costimulation, and cell spreading of T cells. Here we show that immobilized anti-CD82 monoclonal antibody (mAb) as well as anti-alpha4beta1 integrin mAb induced tyrosine phosphorylation of pp105/Crk-associated substrate lymphocyte type (Cas-L) in human peripheral T cells and H9 cells. Furthermore, one of anti-CD82 mAb (8E4), which induces homotypic aggregation of T cells and H9 cells but has no costimulatory activity, partially inhibited very late antigen (VLA)-4 integrin ligand-mediated costimulation of T cells, whereas it failed to inhibit VLA-5 integrin ligand-mediated costimulation. To further elucidate the relationship between CD82- and VLA-4-mediated signaling pathways we defined the IL-2 production by the costimulation of Jurkat T cells with marginal amount of Cas-L, and subsequently found that mAb against CD82 had strong costimulatory activity to CD3/TCR, whereas mAb against beta1 failed to do so in those cells. We have further demonstrated that this discrepancy between beta1 integrin- and CD82-mediated costimulation partly lies in differential activation of NF-AT, AP-1, and NF-kappaB in Jurkat T cells. In this study, although some functional overlap exists, we provide evidence for distinctive signaling of CD82- and beta1 integrin-mediated costimulation at the transcriptional level of IL-2 gene.

Adaptor Proteins, Signal Transducing↗

PubMed2002

A case of intramedullary spinal cord tumor producing human chorionic gonadotropin.

We experienced a case of a persistent trophoblastic disease associated with gradually progressive Brown-Sequard syndrome, which was found to be due to a primary intramedullary spinal cord germinoma with syncytiotrophoblastic giant cells (STGC). We performed both chemotherapy and radiotherapy on separate occasions. Although the chemotherapy appeared to be ineffective, radiotherapy resulted in the disappearance of spinal cord lesions for four years. We reported a case of intramedullary spinal cord germinoma with STGC for which radiotherapy was a better therapeutic modality.

Adult↗

PubMed2002

Temporal profiles of the subcellular localization of Bim, a BH3-only protein, during middle cerebral artery occlusion in mice.

BH3-only proteins are a subfamily of proapoptotic Bcl-2 proteins that act upstream of the mitochondrially mediated cell death pathway, and their association with the pathogenesis of brain ischemia remains largely unknown. The authors explored the temporal profiles of the expression levels and subcellular localization of BH3-only proteins in permanent middle cerebral artery occlusion (MCAO) by Western blot analysis. They observed an increased mitochondrial distribution of Bim at 3 to 6 hours of MCAO that appeared unrelated to transcriptional upregulation, as assessed by semiquantitative reverse transcription-polymerase chain reaction. At 3 to 6 hours of MCAO, Bim immunoreactivity was enhanced in neurons and oligodendrocytes in the ischemic regions. The increased mitochondrial localization of Bim coincided with a marked cytochrome c release and preceded the peak of caspase-9 activation. The authors observed an association of Bim with the dynein intermediate chain, a major component of the dynein motor complex, in the brain using a coimmunoprecipitation assay. Cerebral ischemia induced a time-dependent significant decrease in dynein expression, which started at 3 hours of MCAO. The authors deduced that the liberation of Bim from the dynein motor complex is a likely mechanism for the increased mitochondrial localization of Bim. During MCAO, Bad did not show any change in phosphorylation state or subcellular localization.

Animals↗