Biomedical subjects

T Momoi

Publications and source records attributed to T Momoi.

At least 19 recordsLinked to original sources

PubMed2006

ER stress (PERK/eIF2alpha phosphorylation) mediates the polyglutamine-induced LC3 conversion, an essential step for autophagy formation.

Expanded polyglutamine 72 repeat (polyQ72) aggregates induce endoplasmic reticulum (ER) stress-mediated cell death with caspase-12 activation and vesicular formation (autophagy). We examined this relationship and the molecular mechanism of autophagy formation. Rapamycin, a stimulator of autophagy, inhibited the polyQ72-induced cell death with caspase-12 activation. PolyQ72, but not polyQ11, stimulated Atg5-Atg12-Atg16 complex-dependent microtubule-associated protein 1 (MAP1) light chain 3 (LC3) conversion from LC3-I to -II, which plays a key role in autophagy. The eucaryotic translation initiation factor 2 alpha (eIF2alpha) A/A mutation, a knock-in to replace a phosphorylatable Ser51 with Ala51, and dominant-negative PERK inhibited polyQ72-induced LC3 conversion. PolyQ72 as well as ER stress stimulators upregulated Atg12 mRNA and proteins via eIF2alpha phosphorylation. Furthermore, Atg5 deficiency as well as the eIF2alpha A/A mutation increased the number of cells showing polyQ72 aggregates and polyQ72-induced caspase-12 activation. Thus, autophagy formation is a cellular defense mechanism against polyQ72-induced ER-stress-mediated cell death by degrading polyQ72 aggregates, with PERK/eIF2alpha phosphorylation being involved in polyQ72-induced LC3 conversion.

Adenine↗

PubMed2003

ER stress induces caspase-8 activation, stimulating cytochrome c release and caspase-9 activation.

Excess ER stress induces caspase-12 activation and/or cytochrome c release, causing caspase-9 activation. Little is known about their relationship during ER stress-mediated cell death. Upon ER stress, P19 embryonal carcinoma (EC) cells showed activation of various caspases, including caspase-3, caspase-8, caspase-9, and caspase-12, and extensive DNA fragmentation. We examined the relationship between ER stress-mediated cytochrome c/caspase-9 and caspase-12 activation by using caspase-9- and caspase-8-deficient mouse embryonic fibroblasts and a P19 EC cell clone [P19-36/12 (-) cells] lacking expression of caspase-12. Caspase-9 and caspase-8 deficiency inhibited and delayed the onset of DNA fragmentation but did not inhibit caspase-12 processing induced by ER stress. P19-36/12 (-) cells underwent apoptosis upon ER stress, with cytochrome c release and caspase-8 and caspase-9 activation. The dominant negative form of FADD and z-VAD-fmk inhibited caspase-8, caspase-9, Bid processing, cytochrome c release, and DNA fragmentation induced by ER stress, suggesting that caspase-8 and caspase-9 are the main caspases involved in ER stress-mediated apoptosis of P19-36/12 (-) cells. Caspase-8 deficiency also inhibited the cytochrome c release induced by ER stress. Thus, in parallel with the caspase-12 activation, ER stress triggers caspase-8 activation, resulting in cytochrome c/caspase-9 activation via Bid processing.

Animals↗

PubMed2002

Caspase-12 processing and fragment translocation into nuclei of tunicamycin-treated cells.

Excess endoplasmic reticulum (ER) stress induces processing of caspase-12, which is located in the ER, and cell death. However, little is known about the relationship between caspase-12 processing and cell death. We prepared antisera against putative caspase-12 cleavage sites (anti-m12D318 and anti-m12D341) and showed that overexpression of caspase-12 induced autoprocessing at D(318) but did not induce cell death. Mutation analysis confirmed that D(318) was a unique autoprocessing site. In contrast, tunicamycin, one of the ER stress stimuli, induced caspase-12 processing at the N-terminal region and the C-terminal region (both at D(318) and D(341)) and cell death. Anti-m12D318 and anti-m12D341 immunoreactivities were located in the ER of the tunicamycin-treated cells, and some immunoreactivities were located around and in the nuclei of the apoptotic cells. Thus, processing at the N-terminal region may be necessary for the translocation of processed caspase-12 into nuclei and cell death induced by ER stress. Some of the caspase-12 processed at the N-terminal and C-terminal regions may directly participate in the apoptotic events in nuclei.

Active Transport, Cell Nucleus↗

PubMed2001

Keratin attenuates tumor necrosis factor-induced cytotoxicity through association with TRADD.

Keratin 8 and 18 (K8/18) are the major components of intermediate filament (IF) proteins of simple or single-layered epithelia. Recent data show that normal and malignant epithelial cells deficient in K8/18 are nearly 100 times more sensitive to tumor necrosis factor (TNF)-induced cell death. We have now identified human TNF receptor type 1 (TNFR1)-associated death domain protein (TRADD) to be the K18-interacting protein. Among IF proteins tested in two-hybrid systems, TRADD specifically bound K18 and K14, type I (acidic) keratins. The COOH-terminal region of TRADD interacted with the coil Ia of the rod domain of K18. Endogenous TRADD coimmunoprecipitated with K18, and colocalized with K8/18 filaments in human mammary epithelial cells. Overexpression of the NH2 terminus (amino acids 1-270) of K18 containing the TRADD-binding domain as well as overexpression of K8/18 in SW13 cells, which are devoid of keratins, rendered the cells more resistant to killing by TNF. We also showed that overexpressed NH2 termini of K18 and K8/18 were associated with endogenous TRADD in SW13 cells, resulting in the inhibition of caspase-8 activation. These results indicate that K18 may sequester TRADD to attenuate interactions between TRADD and activated TNFR1 and moderate TNF-induced apoptosis in simple epithelial cells.

Aclarubicin↗

PubMed2001

Expression of RA175 mRNA, a new member of the immunoglobulin superfamily, in developing mouse brain.

RA175, a new member of the immunoglobulin superfamily, is highly expressed during neuronal differentiation of P19 embryonal carcinoma cells. In situ hybridization showed that RA175 mRNA was detected in the developing nervous system, as well as the epithelium of the various non-neuronal tissues of mouse embryo. In contrast with the epithelia of the non-neuronal tissues, RA175 mRNA was not co-expressed with Sonic hedgehog mRNA and Patched mRNA during brain morphogenesis. RA175 mRNA was highly expressed in the anterior horn cells and the peripheral nervous system at embryonic day (E) 11.5 and in the central nervous system at E14.5-E18.5, but its expression decreased after birth and was undetectable in the adult mouse brain.

Aging↗

PubMed2001

Discovery of a novel compound: insight into mechanisms for acrylamide-induced axonopathy and colchicine-induced apoptotic neuronal cell death.

The exposure of humans and experimental animals to certain industrial toxins such as acrylamide is known to cause nerve damage classified as axonopathy, but the mechanisms involved are poorly understood. Here we show that acrylamide induces morphological changes and tyrosine phosphorylation of focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2), a member of the FAK subfamily, in human differentiating neuroblastoma SH-SY5Y cells. Furthermore, we identified a novel molecule designated 'compound-1' that inhibits the morphological and biochemical events. Daily oral administrations of the compound also effectively alleviated behavioral deficits in animals elicited by acrylamide in inclined plane testing, landing foot spread testing and rota-rod performance testing. The compound also effectively inhibited the biological and biochemical responses caused by another axonopathy inducer, colchicine, including tyrosine phosphorylation of Pyk2, formation of an 85-kDa poly(ADP-ribose)polymerase (PARP) fragment and apoptosis-associated induction of the NAPOR gene as well as neuronal cell death. Our findings not only provide insight into FAK and Pyk2 functions in neuronal cells, but may also be important in the development of therapeutic agents for peripheral neuropathy and neurodegeneration.

Acrylamides↗

PubMed2001

Mitosis and apoptosis in postnatal auditory system of the C3H/He strain.

The mouse auditory neurons, hair cells and their supporting cells in the cochlea are considered to be generated mainly in the embryonic days and to be sustained throughout the whole life. In the present study, however, we observed that auditory ganglion cells in the spiral ganglia undergo apoptosis and mitosis in the suckling mouse (1- to 2-week-old C3H/HeJ mice) with a normal auditory system. In spiral ganglia at postnatal days 7 (P7) and 10 (P10), TUNEL (TdT-mediated dUTP nick-end labeling)-positive and morphologically apoptotic ganglion cells were found. Furthermore, by bromodeoxyuridine labeling, mitosis of auditory ganglion cells was found at P10 to P14. In a functional study of auditory brainstem response, we demonstrated that the C3H/HeJ mouse acquires the ability to hear airborne sound at P12 and this is the same time as the opening of their external acoustic meatus (EAM). These results indicate that C3H/HeJ auditory ganglion cells have the ability to proliferate even after opening of the EAM and the initial input of airborne sound. We found that postnatal apoptosis and mitosis after P7 also occurred in the greater epithelial ridge (GER) which is an important organ for maturation of the organ of Corti and is located around the inner hair cells. This indicates that GER cells are not only degenerated but also regenerated until their disappearance around P12. This is the first report on mammals to demonstrate that neuronal mitosis of spiral ganglion cells and that of GER cells occur not only in embryonic and neonatal development but also in postnatal development of the normal auditory system.

Age Factors↗

PubMed2001

Caspase-3-deficiency induces hyperplasia of supporting cells and degeneration of sensory cells resulting in the hearing loss.

Caspase-3 is one of the cystein proteases that play essential roles in programmed cell death. As such, brain development is profoundly affected by caspase-3-deficiency, resulting in hyperplasia and abnormal cell organization (Kuida et al., Nature 1996;384:368-372). In the present study, we used caspase-3 (-/-) mice to show that caspase-3 deficiency results in severe hearing loss, hyperplasia of supporting cells and degeneration of sensory hair cells. The greater epithelial ridge, a remnant of the primordial organ of Corti, persists throughout all of the turns of cochlea in 2-week-old caspase-3 (-/-) mice, which indicates that the morphology of the cochlea is immature. The number of border cells, that develop from the greater epithelial ridge and are one of the supporting cells of the inner hair cell, increase significantly in both 2- and 5-week-old caspase-3 (-/-) mice. On the other hand, abnormal fused stereocilia can be seen in both 2- and 5-week-old caspase-3 (-/-) mice, and disarrangement and loss of sensory hair cells are observed in 5-week-old caspase-3 (-/-) mice. Taken together, both hyperplasia and degeneration occur simultaneously in the inner ear of the caspase-3 (-/-) mice, suggesting that caspase-3-dependent apoptosis is necessary for the development and formation of a properly functioning auditory system in mammals.

Animals↗

PubMed2001

FTY720, a novel immunosuppressive agent, induces apoptosis in human glioma cells.

FTY720, a metabolite from Isaria sinclairii, has been developed to be a potent immunosuppressive drug with induction of apoptosis in T cells and several cell lines. We investigated whether FTY720 induces apoptosis in human glioma cell lines, since they are relatively resistant to multiple apoptotic stimuli. In human glioma cells including T98G, FTY720 induced apoptosiswith ED50 between 1 to 10 microg/ml, while etoposidedid not induce apoptosis at the same doses. Among the caspase family proteases, mainly caspase-6 was activated during the apoptosis by FTY720 but not etoposide. In addition, FTY720 caused tyrosine dephosphorylation of FAK and did not activate a FAK-PI3-kinase survival pathway. This was confirmed also by the observation that orthovanadate prevented FTY720-induced dephosphorylation of FAK and inhibited FTY720-induced cell death. We assumed that FTY720 induced FAK dephosphorylation and cut off the FAK-PI3-kinase pathway resulting in the induction of apoptosis via caspase-6 activation in these glioma cells.

Antineoplastic Agents, Phytogenic↗

PubMed2001

Caspase-11 mediates oligodendrocyte cell death and pathogenesis of autoimmune-mediated demyelination.

Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are inflammatory diseases of the central nervous system (CNS) characterized by localized areas of demyelination. The mechanisms underlying oligodendrocyte (OLG) injury in MS and EAE remain unknown. Here we show that caspase-11 plays crucial roles in OLG death and pathogenesis in EAE. Caspase-11 and activated caspase-3 were both expressed in OLGs in spinal cord EAE lesions. OLGs from caspase-11-deficient mice were highly resistant to the cell death induced by cytotoxic cytokines. EAE susceptibility and cytokine concentrations in the CNS were significantly reduced in caspase-11-deficient mice. Our findings suggest that OLG death is mediated by a pathway that involves caspases-11 and -3 and leads to the demyelination observed in EAE.

Animals↗

PubMed2001

Induction of bud formation of embryonic mouse tracheal epithelium by fibroblast growth factor plus transferrin in mesenchyme-free culture.

Embryonic mouse tracheal epithelium, which branches in an epithelial-mesenchymal recombination culture with bronchial mesenchyme, was cultured under mesenchyme-free conditions. When embedded in a basement-membrane-like matrix and cultured in a serum-free medium supplemented with fibroblast growth factor 1 (FGF1), the tracheal epithelium did not branch, whereas the bronchial epithelium underwent branching morphogenesis. When the medium was enriched with transferrin (Tf), bud formation was induced in the tracheal epithelium and some buds branched secondarily. FGF7 and FGF10, in cooperation with Tf, induced tracheal bud formation to the same extent as FGF1, although the optimum concentrations differed. A bromodeoxyuridine-labeling study comparing cultures with and without Tf showed no Tf-specific amplification of cell proliferation. A whole-mount in situ hybridization study of the expression of Bmp4 and Shh genes in explants of mesenchyme-free culture revealed that both genes were ubiquitously expressed and that expression did not correlate with bud formation. This expression pattern was different from the distally localized expression pattern observed in normal lung rudiments and in extratracheal buds induced by the recombined bronchial mesenchyme. These results suggest that both bronchial and tracheal bud formations were initiated without localized exposure of the epithelium to FGFs and were not accompanied by localized expression of Bmp4 and Shh in the epithelium.

Age Factors↗

PubMed2001

Caspase activity is involved in, but is dispensable for, early motoneuron death in the chick embryo cervical spinal cord.

We examined the role of caspases in the early programmed cell death (PCD) of motoneurons (MNs) in the chick embryo cervical cord between embryonic day (E) 4 and E5. An increase in caspase-3-like activity in MNs was observed at E4.5. Treatment with an inhibitor of caspase-3-like activity, Ac-DEVD-CHO, for 12 h blocked this increase and revealed that caspase-3-like activity is mainly responsible for DNA fragmentation and the nuclear changes during PCD but not for degenerative changes in the cytoplasm. When a more broad-spectrum caspase inhibitor was used (bocaspartyl (OMe)-fluoromethyl ketone, BAF), the appearance of degenerative changes in the cytoplasm was delayed by at least 12 h. However, following treatment with either Ac-DEVD-CHO or BAF for 24 h, the number of surviving healthy MNs did not differ from controls, indicating a normal occurrence of PCD despite the inhibition of caspases. These results suggest that caspase cascades that occur upstream of and are independent of the activation of caspase-3-like activity are responsible for the degenerative changes in the cytoplasm of dying cervical MNs. These data also suggest that, although one function of caspases may be to facilitate the kinetics of PCD, caspases are nonetheless dispensable for at least some forms of normal neuronal PCD in vivo.

Amino Acid Chloromethyl Ketones↗

PubMed2001

Apoptotic morphology does not always require caspase activity in rat cerebellar granule neurons.

The death of a cell via apoptosis is characterized by morphological changes including cell shrinkage and nuclear condensation. Intracellularly, proteases, including caspases, are activated. In the present article we have compared the ability of three different neurotoxic agents to induce caspase activity in cerebellar granule cells (CGC). These compounds are the microtubule-disrupting agent colchicine and the oxidative stress-inducing agents hydrogen peroxide and methylmercury (MeHg). We have previously shown that each of these agents causes nuclear changes that are consistent with apoptosis, i.e., induction of chromatin condensation and DNA cleavage into fragments of regular size (700, 300 and 50 kbp). However, only colchicine causes a large increase in caspase activity, as monitored by the ability of whole cell extracts to cleave the synthetic caspase substrate DEVD-MCA. In contrast, MeHg and hydrogen peroxide do not induce any significant increase of DEVDase activity as compared to control cells. Immunocytochemistry confirms that active caspase-3 is abundant only in colchicine-exposed cells. In agreement with these findings, the pan-caspase inhibitor, z-VAD-fmk, is efficient in protecting CGC against colchicine, but not against hydrogen peroxide or MeHg. These data suggest that in CGC the activation of caspases is not always required to induce morphological changes and pattern of DNA fragmentation consistent with apoptosis.

Journal Article↗

PubMed2001

Cerebrovascular damage in young rabbits after intravenous administration of Shiga toxin 2.

Acute encephalopathy associated with Shiga toxin-producing Escherichia coli (STEC) primarily affects children. To elucidate the age-dependent vulnerability of the central nervous system (CNS), we injected Shiga toxin 2 (Stx2) intravenously to young rabbits and examined the clinical and pathological effects on the CNS. Although neurological disorders caused by Stx2 were similar between young and adult rabbits, the dose required to produce them in the young was one third of that required for the adults. Vascular lesions appeared as early as 24 h after injection in the young, but not at all in the adult. Arteriolar changes, such as hydropic swelling of the endothelial cells and karyorrhexis of the medial cells, were specific to the CNS of young animals. Evidence for apoptosis of vascular cells was scarce because DNA strand breaks and activation of caspases-3 and -9 were absent in the vast majority. Given our results, we conclude that the cerebral blood vessels of immature brains are more vulnerable to Stx2 than those of adults in the rabbit.

Acute Disease↗

PubMed2001

Suppression of hair follicle development inhibits induction of sonic hedgehog, patched, and patched-2 in hair germs in mice.

Embryonic induction of hair follicles is a fascinating model of localized morphogenesis from a simple homogeneous epithelial cell sheet. Accumulating evidence indicates that Sonic hedgehog (Shh) signaling plays a central role in hair follicle formation. We quantitated the expression levels of Shh and its receptor genes, Patched (Ptc) and Patched-2 (Ptch2), in two distinct experimental systems in which the development of hair follicles was suppressed. Shh, Ptc, and Ptch2 were induced about six- to tenfold in normal embryonic hair germs in vivo as well as in developing skin tissue maintained in organ culture. This induction was almost completely inhibited both in the developing skin tissue of ICR mice cultured with 30ng/ml epidermal growth factor and in embryos of Tabby mutant mice (a model of hypohidrotic ectodermal dysplasia) at 14.5-15.5 days postcoitus. Expression of Shh, Ptc and Ptch2 was induced in the Tabby embryos at 16.5 days postcoitus, indicating that Shh signaling may be involved in the formation not only of the well-studied guard hair but also of the awl hair. The potential of the two biological systems for studying molecular mechanisms in hair follicle formation, particularly at an early phase including Shh signaling, is discussed.

Animals↗

PubMed2001

Massive muscle cell degeneration in the early stage of merosin-deficient congenital muscular dystrophy.

Primary merosin-deficient congenital muscular dystrophy (CMD) is a severe form of congenital muscular disorder which is caused by mutations in the laminin alpha2 chain gene (LAMA2). The disease is characterized by marked dystrophic changes in skeletal muscles during early infancy, while little is known about the pathological process of the muscle fiber degeneration. Here, we report the immunohistochemical analysis of skeletal muscle in ten patients with primary merosin-deficient CMD using a panel of molecular markers for skeletal muscle proteins, cellular necrosis, and apoptosis. In the youngest patient (a 52 day old baby), prominent massive muscle cell degeneration occurred in association with the deposition of the C5-9 complement membrane attack complex (MAC). Most of the MAC-positive muscle fibers showed a severely deranged immunoreaction to dystrophin, dystroglycans, and other sarcolemmal proteins. In addition, we found scattered positive signals for apoptosis. Similar but milder changes were also observed in six other patients younger than 1 year. In the patients older than 3 years, muscle fibers positive for MAC and apoptotic signals were barely detectable. These findings imply that massive muscle fiber degeneration occurs in the very early stage of merosin-deficient CMD and may contribute to the severe dystrophic changes in muscle from early infancy.

Biopsy↗

PubMed2001

Localization of activated caspase-3-positive and apoptotic cells in the developing tooth germ of the mouse lower first molar.

This study examined the immunohistochemical detection of activated caspase-3, and its association with apoptosis, during tooth morphogenesis of the mouse lower first molar. The distribution of cells positive for caspase-3 closely corresponded with the localization of the terminal deoxynucleotidyl transferase-mediated deoxyuridine-5'-triphosphate-biotin nick end labelling (TUNEL)-positive apoptotic cells through the developmental course of tooth germs from embryo day 12 (E12) to E19, thus showing that the apoptosis occurring in the developing odontogenic tissue was induced by the activation of the caspase family. The specific distribution pattern of apoptotic cells in the developing odontogenic epithelial tissue from the initiation (E12) of tooth germ to the completion of tooth crown morphology (E19) also suggests that apoptotic events are related not only to a deletion of functionally suspended cells, but also participate in initiation and the completion of tooth morphogenesis. Electron microscopic examination revealed that apoptotic cells were present in the primary enamel knot, and these apoptotic cells were phagocytized by neighbouring odontogenic epithelial cells, thus indicating the prompt disposal of any dead cells by epithelial cells.

Animals↗

PubMed2001

Caspase-9 processing by caspase-3 via a feedback amplification loop in vivo.

In contrast to the autoprocessing of caspase-9, little is known about the biological significance of caspase-9 processing by caspase-3 via a feedback loop in vivo. We prepared antisera against mouse caspase-9 cleavage sites so that only the activated form of mouse caspase-9 was recognized. Using these antisera and caspase-9- and caspase-3-deficient mouse embryonic fibroblasts, we demonstrated that mouse caspase-9 is initially autoprocessed at D(353) and D(368) at low levels during staurosporine-induced apoptosis, whereupon the D(368) and D(168) sites are preferentially processed over D(353) by activated caspase-3 as part of a feedback amplification loop. Ac-DEVD-MCA (caspase-3-like) and Ac-LEHD-MCA (caspase-9-like) cleavage activities clearly showed that caspase-9 autoprocessing was necessary for the activation of caspase-3, whereas full activation of caspase-3 and caspase-9 was achieved only through the feedback amplification loop. This feedback amplification loop also played a predominant role during programmed cell death of dorsal root ganglia neurons at mouse embryonic day 11.5.

Amino Acid Sequence↗