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Biomedical subjects

S Shimohama

Publications and source records attributed to S Shimohama.

At least 91 records · Page 5Linked to original sources
PubMed1998

Alteration of proteins regulating apoptosis, Bcl-2, Bcl-x, Bax, Bak, Bad, ICH-1 and CPP32, in Alzheimer's disease.

Recently, apoptosis has been implicated in the selective neuronal loss of Alzheimer's disease (AD). Apoptosis is regulated by the B cell leukemia-2 gene product (Bcl-2) family (Bcl-2, Bcl-x, Bax, Bak and Bad) and the caspase family (ICH-1 and CPP32), with apoptosis being prevented by Bcl-2 and Bcl-x, and promoted by Bax, Bak, Bad, ICH-1 and CPP32. In the present study, we examined the levels of these proteins in the membranous and cytosolic fractions of temporal cortex in AD and control brain. In the membranous fraction, the levels of Bcl-2 alpha, Bcl-xL, Bcl-x beta, Bak and Bad were increased in AD. In the cytosolic fractions, the level of Bcl-x beta was increased, while Bcl-xL, Bax, Bak, and Bad and ICH-1L were unchanged. CPP32 was not detected in AD or control brain. These findings demonstrate a differential involvement of cell death-regulatory proteins in AD and suggest that Bak, Bad, Bcl-2 and Bcl-x are upregulated in AD brains.

Age Factors↗
PubMed1998

Indication of a protein kinase C-independent pathway for NADPH oxidase activation in human neutrophils.

A potent tyrosine phosphatase inhibitor, pervanadate, induced (i) translocation of the cytosolic NADPH oxidase factors, p47-phox and p67-phox, to the plasma membrane; and (ii) O2- production in human neutrophils. However, the translocation of p47-phox and p67-phox was inhibited by H-7, a protein kinase C (PKC) inhibitor without markedly affecting O2- production in whole neutrophils. Results from the plasma membrane fraction showed that NADPH oxidase activity in neutrophils treated with pervanadate did not vary in the presence or absence of H-7, despite a lower content of p47-phox and p67-phox in H-7-treated neutrophils. These findings suggest that in addition to the well-known PKC-dependent pathway, there may exist another PKC-independent pathway to activate NADPH oxidase in human neutrophils. This pathway involves protein tyrosine phosphorylation but does not seem to necessitate translocation of p47-phox and p67-phox to the plasma membrane.

Enzyme Activation↗
PubMed1998

Nicotinic alpha 7 receptors protect against glutamate neurotoxicity and neuronal ischemic damage.

The alpha7 receptor agonist dimethoxybenzylidene anabaseine (DMXB) protected rat neocortical neurons against excitotoxicity administered 24 h before, but not concomitantly with, NMDA. This action was blocked by nicotinic but not muscarinic antagonists. DMXB (1 mg/kg i.p.) also reduced infarct size in rats when injected 24 h before, but not during, focal ischemic insults. In a mecamylamine-sensitive manner, alpha7 receptors appear neuroprotective in non-apoptotic model.

Animals↗
PubMed1998

Dopamine D2-type agonists protect mesencephalic neurons from glutamate neurotoxicity: mechanisms of neuroprotective treatment against oxidative stress.

Oxidative stress, a process in which neurotoxic oxygen free radicals cause dopaminergic neuronal degeneration, has been implicated in the degenerative process in Parkinson's disease. Glutamate-induced neurotoxicity is a model of oxidative stress. We demonstrated that preincubation with D2-type dopamine agonists bromocriptine and quinpirole provides neuroprotection against glutamate-induced neurotoxicity in cultured rat mesencephalic neurons. Simultaneous administration of D2 agonists, however, did not provide neuroprotection. The protective effects were dependent on the duration of preincubation and were blocked by a D2 antagonist and a protein synthesis inhibitor. Furthermore, preincubation with D2 agonists provided neuroprotection against toxicity induced by calcium overload and exposure to superoxide anions. Confocal microscopic analysis, using 2,7-dichlorofluorescin diacetate, revealed that bromocriptine preincubation suppressed the action of radicals on neurons. These findings indicate that dopamine D2 agonists provide protection mediated not only by the inhibition of dopamine turnover but also via D2-type dopamine receptor stimulation and the subsequent synthesis of proteins that scavenge free radicals.

Animals↗
PubMed1998

Mechanism of selective motor neuronal death after exposure of spinal cord to glutamate: involvement of glutamate-induced nitric oxide in motor neuron toxicity and nonmotor neuron protection.

In this study, we analyzed the mechanism of selective motor neuronal death, a characteristic of amyotrophic lateral sclerosis, using embryonic rat spinal cord culture. When dissociated cultures were exposed to low-level glutamate (Glu) coadministered with the Glu transporter inhibitor L-trans-pyrrolidine-2,4-decarboxylate (PDC) for 24 hours, motor neurons were selectively injured through N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptors. Nitric oxide synthase (NOS) inhibitors attenuated this toxicity, and long-acting nitric oxide (NO) donors damaged motor neurons selectively. Nonmotor neurons survived after exposure to low-dose Glu/PDC, but Glu-induced toxicity was potentiated by coadministration of an NO-dependent guanylyl cyclase inhibitor. In addition, 8-bromo-cyclic GMP, a soluble cyclic GMP analogue, rescued nonmotor neurons, but not motor neurons, exposed to high-dose Glu/PDC. Twenty-four hours' incubation with PDC elevated the number of neuronal NOS-immunoreactive neurons by about twofold compared with controls, and a double-staining study, using the motor neuron marker SMI32, revealed that most of them were nonmotor neurons. These findings suggest that selective motor neuronal death caused by chronic low-level exposure to Glu is mediated by the formation of NO in nonmotor neurons, which inversely protects nonmotor neurons through the guanylyl cyclase-cyclic GMP cascade. Induction of neuronal NOS in nonmotor neurons might enhance both the toxicity of motor neurons and the protection of nonmotor neurons, which could explain the pathology of amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis↗
PubMed1998

Nitric oxide donor-induced p53-sensitive cell death is enhanced by Bcl-2 reduction in human neuroblastoma cells.

In human neuroblastoma SH-SY5Y cells, S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO)-donor, caused cell death accompanying p53 expression, nucleosomal DNA fragmentation and cell death. In addition, SNAP-induced cell death and DNA fragmentation were enhanced by pretreatment for 4 days with N6,2'-O-dibutyryl cyclic AMP (diBu-cAMP) or staurosporine, while those were not changed by pretreatment with phorbol 12-myristate 13-acetate (PMA). Protein level of Bcl-2 was decreased by pretreatment with diBu-cAMP or staurosporine, and, on the contrary, the level was increased by pretreatment with PMA. However, these pretreatments did not change Bax protein level and SNAP-induced p53 expression. However, SNAP-treatment did not change protein levels of Bcl-2 and Bax. These results suggest that SNAP-induced p53-sensitive apoptosis is enhanced by Bcl-2 reduction, and that Bcl-2 and Bax may act downstream of p53 in SH-SY5Y cells.

Animals↗
PubMed1998

myo-Inositol monophosphatase in the brain has zinc ion-dependent tyrosine phosphatase activity.

1. myo-Inositol monophosphatase (E.C. 3.1.3.25) hydrolyzes inositol monophosphate to form free myo-inositol, the precursor for the inositol phospholipid second-messenger signaling systems. The biochemical properties of the enzyme were examined in detail. 2. The enzyme exhibited significant hydrolytic activity only on phosphotyrosine among physiological substrates tested in the presence of Zn2+ ions in an acidic environment. 3. The enzyme was recognized and immunoprecipitated with polyclonal antibodies developed against the Zn2+-dependent tyrosine phosphatase of bovine brain. 4. These results indicate that myo-inositol monophosphatase exhibits Zn2+-dependent tyrosine phosphatase activity in an acidic environment and has immunological identity with a Zn2+-dependent tyrosine phosphatase.

Acid Phosphatase↗
PubMed1998

Phospholipase C isozymes in the human brain and their changes in Alzheimer's disease.

Phosphoinositide-specific phospholipase C is a key enzyme in signal transduction. We have previously demonstrated that an isozyme of phospholipase C, phospholipase C-delta1, accumulates aberrantly in the brains of patients with Alzheimer's disease. In the present study, we examined the property of phospholipase C isozymes in human brains using the methods of chromatofocusing and gel filtration chromatography, and investigated their changes in Alzheimer's disease brains. The chromatofocusing profile of human brain phospholipase C activity on a Mono P HR column demonstrated that phospholipase C-gamma1, exhibiting an isoelectric point value of 5.2, and phospholipase C-delta1, exhibiting isoelectric point values of 5.2 and 4.6, are partly overlapped in their elution. In contrast, the elution profiles of control and Alzheimer's disease brain phospholipase C on Superdex 200 pg column gel filtration chromatography indicated that phospholipase C-gamma1 and phospholipase C-delta1 can be separated with the elution position having a molecular weight of about 240,000 and 140,000, respectively, in the human brain. Using this gel filtration chromatography it was revealed that the phospholipase C-gamma1 activity was significantly decreased and the phospholipase C-delta1 activity was significantly increased in Alzheimer's disease brains compared with controls. These results suggest that the phospholipase C isozymes are differentially involved in Alzheimer's disease.

Aged↗
PubMed1998

Intracellular receptors for activated C-kinase in the postmortem human brain: no alteration in Alzheimer disease.

Previous studies have identified a 36-kDa protein that has the properties of an intracellular receptor for the activated C-kinase (RACK1). In the present investigation we quantified levels of RACK1 protein in brains from patients with Alzheimer disease (AD) and age-matched controls. Western analysis using a specific antibody showed that the protein levels for RACK1 were not significantly different in AD brains than in controls, indicating that RACK1 is preserved in AD.

Aged↗
PubMed1998

Characterization of high- and low-molecular weight zinc-dependent acid phosphatases in bovine liver.

We have purified two forms of Zn2+-dependent acid phosphatase (Zn2+-APase) from bovine liver, both of which require Zn2+ to hydrolyze the substrate p-nitrophenyl phosphate in an acidic environment. The apparent molecular weights of these two forms of Zn2+-APase were estimated to be about 100,000 and 62,000 by gel filtration, and about 44,000 and 31,000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, respectively. The low-molecular weight (LMW) Zn2+-APase catalyzed the hydrolysis of myo-inositol-1-phosphate in the presence of 3 mM Mg2+ at physiological pH, but the high-molecular weight (HMW) enzyme did not. The LMW-Zn2+-APase of bovine liver was recognized by polyclonal antibodies developed against the Zn2+-APase of bovine brain, but the HMW-Zn2+-APase was not.

Acid Phosphatase↗
PubMed1998

Reduction of platelet phospholipase C-delta1 activity in Alzheimer's disease associated with a specific apolipoprotein E genotype (epsilon3/epsilon3).

The epsilon4 allele of apolipoprotein E (apo E) is increased among patients with sporadic or familial Alzheimer's disease (AD). We examined platelet phospholipase C (PLC)-delta1 activity in AD patients either homozygous for apoepsilon3 or having at least one apo epsilon4 allele. We found that platelet PLC-delta1 activity is reduced from control levels in patients homozygous for apo epsilon3, but not changed in patients with an apo epilson4 allele. Reduced PLC-delta1 activity and apo epsilon3 may contribute to AD pathogenesis apart from the apo epsilon4 allele.

Aged↗
PubMed1997

Alteration of transcription factors NF-kappaB and STAT1 in Alzheimer's disease brains.

Recent studies suggest that inflammatory activation occurs in the brains of patients with Alzheimer's disease (AD). Several transcription factors such as nuclear factor-kappaB (NF-kappaB) and signal transducer and activator of transcription-1 (STAT1) may be activated in glial cells by a number of cytokines and then translocated from the cytosol to the nucleus. We assessed NF-kappaB and STAT1 in temporal cortex from normal and AD brains using specific antibodies. NF-kappaB p65 in the particulate fraction and STAT1alpha in both the particulate and cytosolic fractions were more abundant in AD cases than in controls. These findings suggest that the increased NF-kappaB and STAT1alpha in cell nuclei may be involved in inflammatory activation in AD brains.

Aged↗
PubMed1997

Nicotine protects cultured cortical neurons against glutamate-induced cytotoxicity via alpha7-neuronal receptors and neuronal CNS receptors.

We examined the effects of nicotine on glutamate-induced cytotoxicity using primary cultures of rat cortical neurons. The cell viability decreased significantly when cultures were exposed to glutamate for 10 min and then incubated with glutamate-free medium for 1 h. The exposure of cultures to nicotine (10 microM) for 8-24 h prior to glutamate application ameliorated the glutamate-induced cytotoxicity, with no significant effect of nicotine alone on the cell viability. Neuroprotection by nicotine was dependent on the incubation period. alpha-bungarotoxin (alpha-BTX) and methyllycaconitine (MLA), both of which are alpha7-neuronal receptor antagonists, and dihydro-beta-erythroidine (DHbetaE), a neuronal central nervous system (CNS) receptor antagonist, each significantly antagonized the protection by nicotine against glutamate-induced cytotoxicity. Ionomycin, a calcium ionophore, and S-nitrosocysteine (SNOC), a nitric oxide (NO) donor, also induced cytotoxicity in a manner similar to glutamate. Nicotine protected cultures against ionomycin-induced cytotoxicity, but not against SNOC-induced cytotoxicity. These results suggest that nicotine protects cultured cortical neurons against glutamate-induced cytotoxicity via alpha7-neuronal receptors and neuronal CNS receptors by reducing NO-formation triggered by Ca2+ influx.

Aconitine↗
PubMed1997

Activation and involvement of p38 mitogen-activated protein kinase in glutamate-induced apoptosis in rat cerebellar granule cells.

In the mammalian central nervous system glutamate is the major excitatory neurotransmitter and plays a crucial role in plasticity and toxicity of certain neural cells. We found that glutamate stimulated activation of p38 and stress-activated protein kinase (SAPK, also known as c-Jun N-terminal kinase (JNK)), two subgroup members of the mitogen-activated protein kinase superfamily in matured cerebellar granule cells. The p38 activation was largely mediated by N-methyl-D-aspartate receptors. Furthermore, we have revealed a novel signaling pathway, that is, Ca2+-mediated activation of p38 in glutamate-treated granule cells. The glutamate concentration effective for inducing apoptosis correlated with that for inducing p38 activation. SB203580, a specific inhibitor for p38, inhibited glutamate-induced apoptosis. Thus p38 might be involved in glutamate-induced apoptosis in cerebellar granule cells.

Animals↗
PubMed1997

Differential involvement of synaptic vesicle and presynaptic plasma membrane proteins in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by progressive cognitive decline. Recent studies have shown that synaptic loss in the cortex is the major correlate of cognitive decline in AD. In the present study we assessed synaptic proteins such as synaptobrevin, synaptophysin, synaptotagmin, synaptosomal-associated protein 25 (SNAP-25), and syntaxin1/HPC-1 in control and AD brains to determine whether synaptic proteins are equally or differentially affected in AD. Western analysis showed that in AD levels of synaptobrevin and synaptophysin were decreased by some 30% from amounts in controls, while those of synaptotagmin, SNAP-25, and syntaxin 1/HPC-1 were decreased by only about 10%. As synaptobrevin and synaptophysin are localized mainly in transmitter-containing synaptic vesicles while SNAP-25 and syntaxin 1/HPC-1 are found in presynaptic plasma membranes, these results suggest differential involvement of synaptic components in AD.

Alzheimer Disease↗
PubMed1997

BDNF prevents NO mediated glutamate cytotoxicity in cultured cortical neurons.

The effects of brain-derived neurotrophic factor (BDNF) on glutamate-induced cytotoxicity were examined using primary cultures of rat cortical neurons. BDNF induced TrkB tyrosine phosphorylation in rat cultured cortical neurons. The cell viability was significantly reduced when cultures were briefly exposed to glutamate and incubated with normal medium for 24 h. Glutamate cytotoxicity was prevented by MK-801, which is a non-competitive blocker of N-methyl-D-aspartate and N(omega)-nitro-L-arginine, which is a blocker of nitric oxide synthetase. Delayed neurotoxicity was also induced by ionomycin, a calcium ionophore, and nitric oxide (NO) donors such as S-nitrosocysteine (SNOC) and 3-morpholinosydnonimine (SIN-1). Incubating cultures with BDNF for 10 min to 24 h protected cortical neurons against glutamate neurotoxicity. The protective effects of BDNF against glutamate cytotoxicity were dependent on both its concentrations and incubation time. BDNF also prevented the ionomycin-, SNOC-, and SIN-1 induced cytotoxicity. These results indicate that BDNF protects cultured cortical neurons from NMDA receptor-mediated glutamate neurotoxicity by reducing cytotoxic action of NO.

Animals↗
PubMed1997

Changes of p53 in the brains of patients with Alzheimer's disease.

Recent studies suggest that cortical neurons and glial cells undergo apoptosis in Alzheimer's disease (AD). Since the protein p53 is known to induce apoptosis, we assessed p53 in postmortem samples from normal human and AD brains using specific antibody. In AD brains, the amount of p53 in temporal cortex was significantly higher than in controls, and this p53-like immunoreactivity was observed in glial cells. These findings suggest that the p53 may be involved in the apoptosis of glial cells in AD brains, but apoptosis in neurons may occur through a p53-independent pathway.

Aged↗