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Biomedical subjects

Takako Niikura

Publications and source records attributed to Takako Niikura.

At least 19 recordsLinked to original sources

NK4, an antagonist of hepatocyte growth factor (HGF), inhibits growth of multiple myeloma cells: molecular targeting of angiogenic growth factor.

Hepatocyte growth factor (HGF) promotes cell growth and motility and also increases neovascularization. Multiple myeloma (MM) cells produce HGF, and the plasma concentration of HGF is significantly elevated in patients with clinically active MM, suggesting that HGF might play a role in the pathogenesis of MM. NK4, an antagonist of HGF, is structurally homologous to angiostatin, and our previous report showed that NK4 inhibited the proliferation of vascular endothelial cells induced by HGF stimulation. The purposes of this study were to elucidate the contribution of HGF to the growth of MM cells as well as to investigate the possibility of the therapeutic use of NK4. In vitro study showed that NK4 protein stabilized the growth of MM cell lines and regulated the activation of c-MET, ERK1/2, STAT3, and AKT-1. Recombinant adenovirus containing NK4 cDNA (AdCMV.NK4) was injected intramuscularly into Icr/scid mice bearing tumors derived from HGF-producing MM cells. AdCMV.NK4 significantly inhibited the growth of these tumors in vivo. Histologic examination revealed that AdCMV.NK4 induced apoptosis of MM cells, accompanied by a reduction in neovascularization in the tumors. Thus, NK4 inhibited the growth of MM cells via antiangiogenic as well as direct antitumor mechanisms. The molecular targeting of HGF by NK4 could be applied as a novel therapeutic approach to MM.

Animals↗

The secondary structure analysis of a potent Ser14Gly analog of antiAlzheimer peptide, Humanin, by circular dichroism.

The structure of a highly potent Ser14Gly analog of antiAlzheimer peptide, Humanin, was examined by circular dichroism (CD). The secondary structure is more disordered in water than in phosphate-buffered saline (PBS). The peptide structure in water is little dependent on both peptide concentration and temperature. On the contrary, the peptide structure was significantly different in PBS from the structure in water, which is more apparent at a higher peptide concentration and temperature. The observed different structure in PBS appears to be due to self-association of the peptide, which is enhanced by elevated temperature and, hence, via hydrophobic interactions. The wild-type Humanin also behaved similarly, i.e., it assumed a disordered structure in water but underwent conformational changes in PBS. Although high peptide concentrations for CD measurements are not encountered in vivo, the results suggest the tendency of the peptide to interact hydrophobically with other structures as well as with itself.

Alzheimer Disease↗

Implanted cannula-mediated repetitive administration of Abeta25-35 into the mouse cerebral ventricle effectively impairs spatial working memory.

Amyloid beta (Abeta) is closely related to the onset of Alzheimer's disease (AD). To construct AD animal models, a bolus administration of a large dose of toxic Abeta into the cerebral ventricles of rodents has been performed in earlier studies. In parallel, a continuous infusion system via an osmotic pump into the cerebral ventricle has been developed to make a rat AD model. In this study, we developed a mouse AD model by repetitive administration of Abeta25-35 via a cannula implanted into the cerebral ventricle. Using this administration system, we reproducibly constructed a mouse with impaired spatial working memory. In accordance with the occurrence of the abnormal mouse behavior, we found that the number of choline acetyltransferase (ChAT)-positive neurons was reduced in paraventricular regions of brains of Abeta25-35-administered mice in a dose-dependent manner. Considering that the repetitive administration of a small dose of toxic Abeta via an implanted cannula leads to a brain status more resembling that of the AD patients than a bolus injection of a large dose of Abeta, and therapeutic as well as toxic agents are able to be repeatedly and reliably administered via an implanted cannula, we concluded that the implanted cannula-bearing AD mouse model is useful for development of new AD therapy.

Alzheimer Disease↗

Expression of N19S-SOD1, an SOD1 mutant found in sporadic amyotrophic lateral sclerosis patients, induces low-grade motoneuronal toxicity.

Amyotrophic lateral sclerosis (ALS) is the most common fatal motor neuron disease. It has been generally accepted that the proapoptotic property of the familial ALS (FALS)-linked mutant SOD1 genes plays an important role in the pathogenesis of some FALS cases. We found here that expression of N19S-SOD1, a novel SOD1 mutant originally found in a sporadic ALS patient, induces lower grade death in NSC34 cells than FALS-linked mutant SOD1. In agreement, intracytoplasmic aggregate formation and SOD1 polymerization are less prominently induced by ectopic expression of N19S-SOD1 than FALS-linked mutant SOD1. We further found that additional cell stresses, such as inhibition of proteasomal activity or up-regulation of intracellular oxidative stress, enhance N19S-SOD1-induced aggregate formation and polymerization of N19S-SOD1. Such analysis of the intracellular polymerization and the ubiquitination of N19S-SOD1 have further suggested that it is recognized as a misfolded protein, like FALS-linked mutant SOD1, whereas wild-type SOD1 is not. Altogether, it is speculated that the N19S mutation of SOD1 in cooperation with associated cell stresses contributes to the onset of ALS as a risk factor.

Amyotrophic Lateral Sclerosis↗

Involvement of tyrosine kinases and STAT3 in Humanin-mediated neuroprotection.

Humanin (HN) inhibits neuronal cell death induced by various Alzheimer's disease (AD)-related insults. It has been proposed that HN binds to a putative receptor on the cell membrane and triggers a signal transduction cascade linked to neuroprotection. Recently, it was shown that HN binds to pertussis toxin (PTX)-sensitive G protein-coupled formylpeptide receptor-like-1 molecule (FPRL-1), reduces A beta(1--42) aggregation and fibril formation, and suppresses the A beta(1--42) toxicity on mononuclear phagocytic cells [Ying, G., Iribarren, P., Zhou, Y., Gong, W., Zhang, N., Yu, Z.X., Le, Y., Cui, Y., Wang, J.M., 2004. Humanin, a newly identified neuroprotective factor, uses the G protein-coupled formylpeptide receptor-like-1 as a functional receptor. Journal of Immunology 172 (11), 7078--7085.]. We here show that siRNA-mediated disruption of expression of the mouse counterpart of FPRL-1, FPR2, did not result in attenuation of HN-mediated rescue of neuronal cell death induced by AD-related insults. We simultaneously provide evidence that neuroprotection by HN in F11 cells is mediated by the STAT3 transcription factor as well as by certain tyrosine kinases. Altogether, we speculate that a receptor other than FPR2 exists that mediates HN neuroprotection in F11 neurohybrid cells.

Alzheimer Disease↗

A humanin derivative, S14G-HN, prevents amyloid-beta-induced memory impairment in mice.

Humanin (HN) is a 24-amino acid peptide that protects neuronal cells from death caused by Alzheimer's disease (AD)-related genes and amyloid-beta (Abeta). Multiple studies have revealed its biochemical and neuroprotective characteristics in vitro; however, little has been known regarding whether HN is effective in vivo in AD model systems. We examined the effect of S14G-HN, a 1,000-fold more potent derivative of HN in vitro, on amnesia induced by Abeta25-35 in mice. The Y-maze test revealed that at least 50 pmol of S14G-HN by intracerebroventricular injection prevented Abeta-induced impairment of short-term/spatial working memory; however, 5 nmol of S14A-HN, a neuroprotection-defective mutant in vitro, did not prevent Abeta-induced amnesia. These results are in agreement with the structure-function correlation shown previously in vitro. In the water-finding task, S14G-HN prevented prolongation of finding latency (the time to find water) observed in Abeta-amnesic mice, indicating that S14G-HN also blocked Abeta-induced impairment of latent learning. In accordance with these observations, immunohistochemical analysis showed that S14G-HN sustained the number of cholinergic neurons in the basal forebrain and the striata nearly to the normal level. Furthermore, genistein, a specific inhibitor of tyrosine kinases, blocked recovery from scopolamine-induced amnesia by S14G-HN, suggesting that certain tyrosine kinase(s) are involved in the inhibitory function of S14G-HN in vivo. Taking these findings together, we conclude that S14G-HN has rescue activity against memory impairment caused by AD-related insults in vivo by activating the same intracellular neuroprotective machinery as elucidated previously in vitro.

Amnesia↗

Neuroprotective effect of activity-dependent neurotrophic factor against toxicity from familial amyotrophic lateral sclerosis-linked mutant SOD1 in vitro and in vivo.

Amyotrophic lateral sclerosis (ALS) is the most common fatal motor neuron disease, affecting mostly middle-aged people. There are no curative therapies for ALS. Several lines of evidence have supported the notion that the proapoptotic property of familial ALS (FALS)-linked mutant Cu/Zn-superoxide dismutase-1 (SOD1) genes may play an important role in the pathogenesis of some FALS cases. Here we found that activity-dependent neurotrophic factor (ADNF), a neurotrophic factor originally identified to have the anti-Alzheimer's disease (AD) activity, protected against neuronal cell death caused by FALS-linked A4T-, G85R- and G93R-SOD1 in a dose-responsive fashion. Notably, ADNF-mediated complete suppression of SOD1 mutant-induced neuronal cell death occurs at concentrations as low as 100 fM. ADNF maintains the neuroprotective activity even at concentrations of more than 1 nM. This is in clear contrast to the previous finding that ADNF loses its protective activity against neurotoxicity induced by AD-relevant insults, including some familial AD genes and amyloid beta peptide at concentrations of more than 1 nM. Characterization of the neuroprotective activity of ADNF against cell death caused by SOD1 mutants revealed that CaMKIV and certain tyrosine kinases are involved in ADNF-mediated neuroprotection. Moreover, in vivo studies showed that intracerebroventricularly administered ADNF significantly improved motor performance of G93A-SOD1 transgenic mice, a widely used model of FALS, although survival was extended only marginally. Thus, the neuroprotective activity of ADNF provides a novel insight into the development of curative drugs for ALS.

Age of Onset↗

Cytotoxic mechanisms by M239V presenilin 2, a little-analyzed Alzheimer's disease-causative mutant.

Although neurotoxic functions are well characterized in familial Alzheimer's disease (FAD)-linked N141I mutant of presenilin (PS)2, little has been known about M239V-PS2, another established FAD-causative mutant. We found that expression of M239V-PS2 caused neuronal cytotoxicity. M239V-PS2 exerted three forms of cytotoxicity: one was sensitive to both an antioxidant glutathione-ethyl-ester (GEE) and a caspase inhibitor Ac-DEVD-CHO (DEVD); the second was sensitive to GEE but resistant to DEVD; and the third was resistant to both. The GEE/DEVD-sensitive cytotoxicity by M239V-PS2 was likely through NADPH oxidase and the GEE-sensitive/DEVD-resistant cytotoxicity through xanthine oxidase (XO). Both mechanisms by M239V-PS2 were suppressed by pertussis toxin (PTX) and were mediated by Galpha(o), but not by Galpha(i). Although Abeta1-43 itself induced no cytotoxicity, Abeta1-43 potentiated all three components of M239V-PS2 cytotoxicity. As these cytotoxic mechanisms by M239V-PS2 are fully shared with N141I-PS2, they are most likely implicated in the pathomechanism of FAD by PS2 mutations. Notably, cytotoxicity by M239V-PS2 could be inhibited by the combination of two clinically usable inhibitors of superoxide-generating enzymes, apocynin and oxypurinol.

Alzheimer Disease↗

Characterization of V642I-AbetaPP-induced cytotoxicity in primary neurons.

Amyloid precursor protein (AbetaPP), a precursor of amyloid beta (Abeta) peptide, is one of the molecules involved in the pathogenesis of Alzheimer's disease (AD). Specific mutations in AbetaPP have been found in patients inheriting familial AD (FAD). These mutant AbetaPP proteins cause cell death in neuronal cell lines in vitro, but the molecular mechanism of cytotoxicity has not yet been clarified completely. We analyzed the cytotoxic mechanisms of the London-type AbetaPP mutant, V642I-AbetaPP, in primary cortical neurons utilizing an adenovirus-mediated gene transfer system. Expression of V642I-AbetaPP protein induced degeneration of the primary neurons. This cytotoxicity was blocked by pertussis toxin, a specific inhibitor for heterotrimeric G proteins, Go/i, and was suppressed by an inhibitor of caspase-3/7 and an antioxidant, glutathione ethyl ester. A specific inhibitor for NADPH oxidase, apocynin, but not a xanthine oxidase inhibitor or a nitric oxide inhibitor, blocked V642I-AbetaPP-induced cytotoxicity. Among mitogen-activated protein kinase (MAPK) family proteins, c-Jun N-terminal kinase (JNK) and p38MAPK, but not extracellular regulated kinase (ERK), were involved in this cytotoxic pathway. The V642I-AbetaPP-induced cytotoxicity was not suppressed by two secretase inhibitors, suggesting that Abeta does not play a major role in this cytotoxicity. Two neuroprotective factors, insulin-like growth factor I (IGF-I) and Humanin, protected these primary neurons from V642I-AbetaPP-induced cytotoxicity. Furthermore, interleukin-6 and -11 also attenuated this cytotoxicity. This study demonstrated that the signaling pathway activated by mutated AbetaPP in the primary neurons is the same as that by the other artificial insults such as antibody binding to AbetaPP and the artificial dimerization of cytoplasmic domain of AbetaPP. The potential of neurotrophic factors and cytokines in AD therapy is also indicated.

Alzheimer Disease↗

Alsin, the product of ALS2 gene, suppresses SOD1 mutant neurotoxicity through RhoGEF domain by interacting with SOD1 mutants.

Mutation of the ALS2 gene encoding alsin is linked to the onset of autosomal recessive motor neuron diseases, including juvenile-onset amyotrophic lateral sclerosis (ALS). Alsin long form (LF) belongs to the family of the guanine nucleotide exchanging factor (GEF) for small GTPases. Expression of alsin LF, but not alsin short form, protected motor neuronal cells from toxicity induced by mutants of the Cu/Zn-superoxide dismutase (SOD1) gene, which cause autosomal dominant ALS. In contrast, expression of alsin did not suppress neurotoxicity by other neurodegenerative insults such as Alzheimer's disease-related genes. Deletion analysis of alsin LF demonstrated that the RhoGEF domain is essential for alsin-mediated neuroprotection. Furthermore, we found that alsin LF bound to SOD1 mutants, but not to wtSOD1, via the RhoGEF domain. Such functional and physical interaction between two ALS-related genes will become a promising clue to clarify the pathogenesis of ALS and other motor neuron diseases.

Africa, Northern↗

Amino- and carboxyl-terminal mutants of presenilin 1 cause neuronal cell death through distinct toxic mechanisms: Study of 27 different presenilin 1 mutants.

Presenilin (PS)1 and its mutants, which consist of the N-terminal and C-terminal fragments, cause certain familial forms of Alzheimer's disease (FAD). Our earlier studies found that FAD-linked M146L-PS1 causes neuronal cell death through nitrogen oxide synthase (NOS) and that FAD-linked N141I-PS2, another member of the PS family, causes neuronal cell death through NADPH oxidase. In this study, we examined 27 different FAD-linked mutants of PS1, and found that PS1 mutants with mutations in the N-terminal fragment caused NOS inhibitor (NOSI)-sensitive neuronal cell death; in contrast, the PS1 mutants with mutations in the C-terminal fragment caused NOSI-resistant neuronal cell death. The former toxicity was resistant to the specific NADPH oxidase inhibitor apocynin and was inhibited by Humanin (HN), a newly identified neuroprotective factor against Alzheimer's disease (AD)-relevant insults, but not by insulin-like growth factor-I (IGF-I). In contrast, the latter toxicity was sensitive to apocynin and inhibited by both IGF-I and HN. This study indicates for the first time that N- and C-terminal fragment PS1 mutants can generate distinct neurotoxic signals, which will provide an important clue to the understanding of the entire array of neurotoxic signals generated by FAD-causative mutations of PS1.

Acetophenones↗

The Gtx homeodomain transcription factor exerts neuroprotection using its homeodomain.

Certain cases of familial Alzheimer's disease are caused by mutants of amyloid-beta precursor protein (AbetaPP), including V642I-AbetaPP, K595N/M596L-AbetaPP (NL-AbetaPP), A617G-AbetaPP, and L648P-AbetaPP. By using an unbiased functional screening with transfection and expression of a human brain cDNA library, we searched for genes that protect neuronal cells from toxicity by V642I-AbetaPP. One protective clone was identical to the human GTX, a neuronal homeobox gene. Human Gtx (hGtx) inhibited caspase inhibitor-sensitive neuronal cell death not only by V642I-AbetaPP but also by L648P-, NL-, A617G-AbetaPP, apolipoprotein E4, and Abeta. The region of hGtx responsible for this rescue function was specified to be its homeodomain (Lys148-His207). The rescue function was shared by DLX4, a distal-less family gene with a homeodomain only 38.3% homologous to that of hGtx, suggesting that this function would be generally shared by homeodomains. The neuroprotective function of hGtx was attributable to hGtx-stimulated production and secretion of insulin-like growth factor-I. This study provides molecular clues to understand how neuronal cells developmentally regulate themselves against cell death as well as to develop reagents effective in curative therapeutics of Alzheimer's disease.

Alzheimer Disease↗

Humanin antagonists: mutants that interfere with dimerization inhibit neuroprotection by Humanin.

The 24-residue peptide Humanin (HN) protects neuronal cells from insults of various Alzheimer's disease (AD) genes and Abeta by forming a homodimer. We have previously shown that P3A, S7A, C8A, L9A, L12A, T13A, S14A and P19A mutations nullify the neuroprotective function of HN [Yamagishi, Y., Hashimoto, Y., Niikura, T. & Nishimoto, I. (2003) Peptides, 24, 585-595]. Here we examined whether any of these 'null' mutants could function as dominant-negative mutants. Homodimerization-defective mutants, P3A-, L12A-, S14A- and P19A-HN, specifically blocked neuroprotection by HN, but not by activity-dependent neurotrophic factor. Furthermore, insertion of S7A, the mutation that blocks the homodimerization of HN, but not insertion of G5A abolished the antagonizing function of L12A-HN. While L12A-HN and G5A/L12A-HN actually inhibited HN homodimerization, S7A/L12A-HN had no effect. These data indicate that P3A-, L12A-, S14A- and P19A-HN function as HN antagonists by forming an inactive dimer with HN. This study provides a novel insight into the understanding of the in vivo function of HN, as well as into the development of clinically applicable HN neutralizers.

Amyloid beta-Peptides↗

Molecular characterization of neurohybrid cell death induced by Alzheimer's amyloid-beta peptides via p75NTR/PLAIDD.

One of the most important pathological features of Alzheimer's disease (AD) is extracellular senile plaques, whose major component is amyloid-beta peptides (Abeta). Abeta binds to the extracellular domain of p75NTR (p75 neurotrophin receptor) and induces neuronal cell death. We investigated the molecular mechanism of Abeta-induced neurotoxicity in detail from the standpoint of interaction between p75NTR and its recently identified relative, PLAIDD (p75-like apoptosis-inducing death domain). Using F11 neuronal hybrid cells, we demonstrate that there are two distinct pathways for Abeta-induced toxicity mediated by p75NTR. One pathway that has been previously elucidated, is mediated by p75NTR, Go, JNK, NADPH oxidase and caspase3-related caspases. We found that PLAIDD and Gi proteins, heterotrimeric G proteins, are involved in the alternative Abeta-induced neurotoxicity mediated by p75NTR. The alternative pathway triggered by Abeta is thus mediated by p75NTR, PLAIDD, Gi, JNK, NADPH oxidase and caspase3-related caspases. In addition, we found that HN, ADNF, IGF-I, or bFGF inhibits both pathways of Abeta-induced neurotoxicity mediated by p75NTR.

Alzheimer Disease↗

Humanin: after the discovery.

Humanin (HN) is a novel neuroprotective factor that consists of 24 amino acid residues. HN suppresses neuronal cell death caused by Alzheimer's disease (AD)-specific insults, including both amyloid-beta (betaAbeta) peptides and familial AD-causative genes. Cerebrovascular smooth muscle cells are also protected from Abeta toxicity by HN, suggesting that HN affects both neuronal and non-neuronal cells when they are exposed to AD-related cytotoxicity. HN peptide exerts a neuroprotective effect through the cell surface via putative receptor(s). HN activates a cellular signaling cascade that intervenes (at least) in activation of c-Jun N-terminal kinase. The highly selective effect of HN on AD-relevant cell death indicates that HN is promising for AD therapy. Additionally, a recent study showed that intracellularly overexpressed HN suppressed mitochondria-mediated apoptosis by inhibiting Bax activity.

Amino Acid Sequence↗

Interaction between the Alzheimer's survival peptide humanin and insulin-like growth factor-binding protein 3 regulates cell survival and apoptosis.

Insulin-like growth factor-binding protein-3 (IGFBP-3) regulates IGF bioactivity and also independently modulates cell growth and survival. By using a yeast two-hybrid screen to identify IGFBP-3-interacting proteins, we cloned humanin (HN) as an IGFBP-3-binding partner. HN is a 24-aa peptide that has been shown to specifically inhibit neuronal cell death induced by familial Alzheimer's disease mutant genes and amyloid-beta (Abeta). The physical interaction of HN with IGFBP-3 was determined to be of high affinity and specificity and was confirmed by yeast mating, displaceable pull-down experiments with (His)-6-tagged HN, and ligand blot experiments. Co-immunoprecipitation of IGFBP-3 and HN from mouse testes confirmed the interaction in vivo. In cross-linking experiments, HN bound IGFBP-3 but did not compete with IGF-I-IGFBP-3 binding; competitive ligand dot blot experiments revealed the 18-aa heparin-binding domain of IGFBP-3 as the binding site for HN. Alanine scanning determined that F6A-HN mutant does not bind IGFBP-3. HN but not F6A-HN inhibited IGFBP-3-induced apoptosis in human glioblastoma-A172. In contrast, HN did not suppress IGFBP-3 response in SH-SY5Y neuroblastoma and mouse cortical primary neurons. In primary neurons, IGFBP-3 markedly potentiated HN rescue ability from Abeta1-43 toxicity. In summary, we have identified an interaction between the survival peptide HN and IGFBP-3 that is pleiotrophic in nature and is capable of both synergistic and antagonistic interaction. This interaction may prove to be important in neurological disease processes and could provide important targets for drug development.

Alanine↗

Analysis of neurons created from wild-type and Alzheimer's mutation knock-in embryonic stem cells by a highly efficient differentiation protocol.

It is impossible to obtain and amplify live neurons from Alzheimer's disease (AD) patients. To establish the neurons harboring AD abnormality, we constructed mouse embryonic stem (ES) cells, in which the AD-causative V642I mutation was introduced to the endogenous amyloid precursor protein (APP) gene, in combination with a protocol to efficiently differentiate ES cells into postmitotic neurons without using a cell sorter. By this protocol, ES cells differentiated into >90% of the central type of adult postmitotic neurons. Neurons derived from V642I-APP knock-in ES cells were indistinguishable from wild-type ES-derived neurons, as determined by the expression of various markers for neuronal differentiation. Notably, V642I-APP knock-in ES cell-derived neurons exhibited significantly increased secretion of Abeta42 without AD-related hyperphosphorylation of tau, indicating that the direct output of the AD-causative mutation is increased Abeta42 secretion. In this study, we analyze created neurons with wild-type and AD genotypes and propose a new strategy for generating neurons for any dominantly inherited neurodegenerative diseases. The strategy can be applied to create human neurons with AD or any other neurodegenerative disease by using human ES cells.

Alzheimer Disease↗

Characterization of the toxic mechanism triggered by Alzheimer's amyloid-beta peptides via p75 neurotrophin receptor in neuronal hybrid cells.

Neuronal pathology of the brain with Alzheimer's disease (AD) is characterized by numerous depositions of amyloid-beta peptides (Abeta). Abeta binding to the 75-kDa neurotrophin receptor (p75NTR) causes neuronal cell death. Here we report that Abeta causes cell death in neuronal hybrid cells transfected with p75NTR, but not in nontransfected cells, and that p75NTR(L401K) cannot mediate Abeta neurotoxicity. We analyzed the cytotoxic pathway by transfecting pertussis toxin (PTX)-resistant G protein alpha subunits in the presence of PTX and identified that Galpha(o), but not Galpha(i), proteins are involved in p75NTR-mediated Abeta neurotoxicity. Further investigation suggested that Abeta neurotoxicity via p75NTR involved JNK, NADPH oxidase, and caspases-9/3 and was inhibited by activity-dependent neurotrophic factor, insulin-like growth factor-I, basic fibroblast growth factor, and Humanin, as observed in primary neuron cultures. Understanding the Abeta neurotoxic mechanism would contribute significantly to the development of anti-AD therapies.

Alzheimer Disease↗