Apoptosis in subicular neurons: A comparison between suicide and Addison's disease

BACKGROUND

Stress and depression shows possible links to neuronal death in hippocampus. Subiculum plays a prominent role in limbic stress integration and direct effect of corticosteroids on subicular neurons needs to be defined to assess its subsequent impact on hippocampal plasticity.

AIM

This study was intended to assess apoptosis in subicular neurons of a young depressed suicide victim, where presumably stress induced excess of corticosteroids and a case of young Addison's disease with low level of corticosteroids.

MATERIALS AND METHOD

Both bilateral adrenal glands (Addison's) and subiculum (both cases) were initially stained with hematoxylin and eosin; subicular neurons of both cases were examined for the degree of apoptosis using 'ApopTag Kit'. Apoptotic cell counts were expressed as average number of labeled cells/mm 2 and the results were analysed statistically using a non-parametric Mann-Whitney U test.

RESULT

Apoptotic neurons were detected in the subicular region of both suicide and Addison victims, and it is statistically significant in both right and left between the cases (P < 0.05). In suicide victim, the neuronal apoptosis is considerably significant between the two hemispheres (P < 0.05), in contrast to Addison disease where the number of neuronal cell death between right and left was statistically insignificant (P > 0.05).

CONCLUSION

The present study confirms the vulnerability of the subicular neurons to apoptosis, possibly due to corticosteroids in both ends of spectrum.

Mitochondrial dysfunction induces aberrant insulin signalling and glucose utilisation in murine C2C12 myotube cells

AIMS/HYPOTHESIS

Mitochondrial dysfunction is considered a critical component in the development of diabetes. The aim of this study was to elucidate the molecular mechanisms involved in the development of insulin resistance and diabetes through investigation of mitochondrial retrograde signalling.

MATERIALS AND METHODS

Mitochondrial function of C2C12 myotube cells was impaired by genetic (ethidium bromide) and metabolic (oligomycin) stress, and changes in target molecules related to insulin signalling were analysed.

RESULTS

Concomitant with reductions in mitochondrial membrane potential (DeltaPsim) and ATP synthesis, production of IRS1 and solute carrier family 2 (facilitated glucose transporter), member 4 (SLC2A4, formerly known as GLUT4) were reduced. Moreover, serine phosphorylation of IRS1 increased, resulting in decreased tyrosine phosphorylation. This indicates that mitochondrial dysfunction decreases insulin-stimulated SLC2A4 translocation and glucose uptake. Mitochondrial stress activated c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) signalling in a Ca(2+)-dependent manner, and removal of free Ca(2+) by BAPTA-AM, as well as inhibition of JNK and p38 MAPK, abrogated mitochondrial stress-induced reductions in IRS1 and SLC2A4 production. Mitochondrial dysfunction after oligomycin treatment significantly increased levels of activating transcription factor 3 (ATF3), which represses Irs1 promoter activity. Removal of the 5' flanking region of Irs1 demonstrated that the promoter region within 191 bases from the transcription site may be involved in the transcriptional repression of Irs1 by mitochondrial stress.

CONCLUSIONS/INTERPRETATION

We show distinct mitochondrial retrograde signalling, where Irs1 is downregulated through ATF3 in a Ca(2+)-, JNK- and p38 MAPK-dependent manner, and IRS1 is inactivated. Therefore, mitochondrial dysfunction causes aberrant insulin signalling and abnormal utilisation of glucose, as observed in many insulin resistance states.

Estrogen attenuates cell death induced by carboxy-terminal fragment of amyloid precursor protein in PC12 through a receptor-dependent pathway

In the present study, we investigated effects of estrogen on cell death induced by carboxy-terminal fragment of amyloid precursor protein (CT), a candidate causative substance in the pathogenesis of Alzheimer's disease. 17 beta-Estradiol attenuated CT-induced cell death in PC12 cells, whereas 17 alpha-estradiol, nonestrogenic stereoisomer, did not exert any significant protective effect on CT-induced cell death. These results suggest that protective effects of estrogen may be mediated by estrogen receptor (ER) in PC12 cells. To confirm the results, we determined the effects of tamoxifen, an estrogen receptor antagonist. Tamoxifen blocked the protective effects of 17 beta-estradiol, although it did not affect those of 17 alpha-estradiol. Overall, it might be thought that the protective effect of estradiol on CT-induced cell death is achieved by hormonal properties mediated through the estrogen receptor rather than the structural properties as a reducing agent.

C-terminal fragment of amyloid precursor protein induces astrocytosis

One of the pathophysiological features of Alzheimer's disease is astrocytosis around senile plaques. Reactive astrocytes may produce proinflammatory mediators, nitric oxide, and subsequent reactive oxygen intermediates such as peroxynitrites. In the present study, we investigated the possible role of the C-terminal fragment of amyloid precursor protein (CT-APP), which is another constituent of amyloid senile plaque and an abnormal product of APP metabolism, as an inducer of astrocytosis. We report that 100 nM recombinant C-terminal 105 amino acid fragment (CT105) of APP induced astrocytosis morphologically and immunologically. CT105 exposure resulted in activation of mitogen-activated protein kinase (MAPK) pathways as well as transcription factor NF-kappaB. Pretreatment with PD098059 and/or SB203580 decreased nitric oxide (NO) production and nuclear factor-kappa B (NF-kappaB) activation. But inhibitors of NF-kappaB activation did not affect MAPKs activation whereas they abolished NO production and attenuated astrocytosis. Furthermore, conditioned media derived from CT105-treated astrocytes enhanced neurotoxicity and pretreatment with NO and peroxynitrite scavengers attenuated its toxicity. These suggest that CT-APP may participate in Alzheimer's pathogenesis through MAPKs- and NF-kappaB-dependent astrocytosis and iNOS induction.

Effects of the beta-amyloid and carboxyl-terminal fragment of Alzheimer's amyloid precursor protein on the production of the tumor necrosis factor-alpha and matrix metalloproteinase-9 by human monocytic THP-1

To explore the direct role of beta-amyloid (Abeta) and carboxyl-terminal fragments of amyloid precursor protein in the inflammatory processes possibly linked to neurodegeneration associated with Alzheimer's disease, the effects of the 105-amino acid carboxyl-terminal fragment (CT(105)) of amyloid precursor protein on the production of tumor necrosis factor-alpha (TNF-alpha) and matrix metalloproteinase-9 (MMP-9) were examined in a human monocytic THP-1 cell line and compared with that of Abeta. CT(105) elicited a marked increase in TNF-alpha and MMP-9 production in the presence of interferon-gamma in a dose- and time-dependent manner. Similar patterns were obtained with Abeta despite its low magnitude of induction. Autocrine TNF-alpha is likely to be a main mediator of the induction of MMP-9 because the neutralizing antibody to TNF-alpha inhibits MMP-9 production. Genistein, a specific inhibitor of tyrosine kinase, dramatically diminished both TNF-alpha secretion and subsequent MMP-9 release in response to CT(105) or Abeta. Furthermore, PD98059 and SB202190, specific inhibitors of ERK or p38 MAPK respectively, efficiently suppressed CT(105)-induced effects whereas only PD98059 was effective at reducing Abeta-induced effects. Our results suggest that CT(105) in combination with interferon-gamma might serve as a more potent activator than Abeta in triggering inflammatory processes and that both tyrosine kinase and MAPK signaling pathways may represent potential therapeutic targets for the control of Alzheimer's disease progression.

Use-dependent effects of amyloidogenic fragments of (beta)-amyloid precursor protein on synaptic plasticity in rat hippocampus in vivo

The Alzheimer's disease-related beta-amyloid precursor protein (beta-APP) is metabolized to a number of potentially amyloidogenic peptides that are believed to be pathogenic. Application of relatively low concentrations of the soluble forms of these peptides has previously been shown to block high-frequency stimulation-induced long-term potentiation (LTP) of glutamatergic transmission in the hippocampus. The present experiments examined how these peptides affect low-frequency stimulation-induced long-term depression (LTD) and the reversal of LTP (depotentiation). We discovered that beta-amyloid peptide (Abeta1-42) and the Abeta-containing C -terminus of beta-APP (CT) facilitate the induction of LTD in the CA1 area of the intact rat hippocampus. The LTD was frequency- and NMDA receptor-dependent. Thus, although low-frequency stimulation alone was ineffective, after intracerebroventricular injection of Abeta1-42, it induced an LTD that was blocked by d-(-)-2-amino-5-phosphonopentanoic acid. Furthermore, an NMDA receptor-dependent depotentiation was induced in a time-dependent manner, being evoked by injection of CT 10 min, but not 1 hr, after LTP induction. These use- and time-dependent effects of the amyloidogenic peptides on synaptic plasticity promote long-lasting reductions in synaptic strength and oppose activity-dependent strengthening of transmission in the hippocampus. This will result in a profound disruption of information processing dependent on hippocampal synaptic plasticity.

CD99 regulates the transport of MHC class I molecules from the Golgi complex to the cell surface

The down-regulation of surface expression of MHC class I molecules has recently been reported in the CD99-deficient lymphoblastoid B cell line displaying the characteristics of Hodgkin's and Reed-Sternberg phenotype. Here, we demonstrate that the reduction of MHC class I molecules on the cell surface is primarily due to a defect in the transport from the Golgi complex to the plasma membrane. Loss of CD99 did not affect the steady-state expression levels of mRNA and protein of MHC class I molecules. In addition, the assembly of MHC class I molecules and the transport from the endoplasmic reticulum to the cis-Golgi occurred normally in the CD99-deficient cells, and no difference was detected between the CD99-deficient and the control cells in the pattern and degree of endocytosis. Instead, the CD99-deficient cells displayed the delayed transport of newly synthesized MHC class I molecules to the plasma membrane, thus causing accumulation of the molecules within the cells. The accumulated MHC class I molecules in the CD99-deficient cells were colocalized with alpha-mannosidase II and gamma-adaptin in the Golgi compartment. These results suggest that CD99 may be associated with the post-Golgi trafficking machinery by regulating the transport to the plasma membrane rather than the endocytosis of surface MHC class I molecules, providing a novel mechanism of MHC class I down-regulation for immune escape.

Subcellular localization of presenilins during mouse preimplantation development

The genes defective in familial Alzheimer's disease encode the proteins presenilin 1 and 2 (PS1 and 2). Expression of presenilins (PSs) and their proteolytic processing are regulated during neuronal development. Even though these proteins are detected and regulated mainly in Golgi and endoplasmic reticulum, their subcellular distribution during the development is not known. The present study aimed to investigate the localization of PSs and their role during early developmental stage using mouse embryo model. At preimplantation stage, PSs were detected not only in cytoplasm, but also in the nucleus from oocyte to 2.5 dpc (day postcoitum), then disappeared in the nucleus at blastocyst stage (3.5 dpc). Antisense against PS1 and PS2 decreased the transition to blastocyst stage, whereas each antisense alone had no effect. Treatment with lactacystin (26S proteosome inhibitor), which arrest cell cycle at M phase, redistributed PSs into centrosome-kinetochore microtubule. PS2 overexpression in HEK 293 cell arrested cell cycle at S phase. These data suggest that PSs play key roles in cell division and differentiation during early development.

Toxic effect of the beta-amyloid precursor protein C-terminus fragment and Na+/Ca2+ gradients

There is evidence to suggest that certain metabolic fragments of the beta-amyloid precursor protein (betaAPP) containing the whole of the beta-amyloid (Abeta) sequence are toxic to cells. We showed previously that the 105-amino acid C-terminal peptide (CT105) fragment, incorporating Abeta, is particularly toxic to Xenopus oocytes as well as to mammalian neurons. Here, we investigated the contributions of Na+ and Ca2+ gradients to intracellular CT105-induced toxicity in oocytes, monitored by measuring the membrane resting potential. The concentration gradients of Na+ and Ca2+ were manipulated to determine the involvement of the trans-membrane concentration gradients of these ions in the mode of action of CT105. The results suggested that Na+ influx and intracellular events are mainly responsible for the observed CT105-induced toxicity.

Regulation of cytokine production by exogenous nitric oxide in murine splenocyte and peritoneal macrophage

Nitric oxide (NO), products of activated macrophages, have a great impact on the regulation of cytokine production. The role of NO in non-specific host cells is commonly accepted. On the contrary, its role as an immuno-regulatory molecule is still controversial. In this study, we have investigated the effect of NO on the production of cytokines from murine splenocytes and macrophages. S-nitroso-L-glutathione inhibited the release of both interferone-gamma and interleukin-2 produced by Th1 cells and tumor necrosis factor-alpha and interleukin-1beta produced by macrophages, but did not affect the release of interleukin-4 and interleukin-10 produced by Th2 cells. These results suggest that NO exerts a down-regulatory effect on the secretion of cytokines from Th1 cells and macrophages which are implicated in immune response. Thus, NO may have an important role as an immuno-modulatory as well as effector molecule in the immune system.

Carboxyl-terminal fragment of Alzheimer's APP destabilizes calcium homeostasis and renders neuronal cells vulnerable to excitotoxicity

Numerous lines of evidence indicate that some of the neurotoxicity associated with Alzheimer's disease (AD) is due to proteolytic fragments of the amyloid precursor protein (APP). Most research has focused on the amyloid beta peptide (Abeta). However, the possible role of other cleaved products of APP is less clear. We have previously shown that a recombinant carboxy-terminal 105 amino acid fragment (CT 105) of APP induced strong nonselective inward currents in Xenopus oocyte; it also revealed neurotoxicity in PC12 cells and primary cortical neurons, blocked later phase of long-term potentiation in rat hippocampus in vivo, and induced memory deficits and neuropathological changes in mice. We report here that the pretreatment with CT 105 for 24 h at a 10 microM concentration increases intracellular calcium concentration by about twofold in SK-N-SH and PC 12 cells, but not in U251 cells, originated from human glioblastoma. In addition, the calcium increase and toxicity induced by CT 105 were reduced by cholesterol and MK 801 in SK-N-SH and PC 12 cells, whereas the toxicity of Abeta(1-42) was attenuated by nifedipine and verapamil. CT 105 rendered SK-N-SH cells and rat primary cortical neurons more vulnerable to glutamate-induced excitotoxicity. Also, conformational studies using circular dichroism experiments showed that CT 105 has approximately 15% of beta-sheet content in phosphate buffer and aqueous 2,2, 2-trifluoroethanol solutions. However, the content of beta-sheet conformation in dodecyl phosphocholine micelle or in the negatively charged vesicles, is increased to 22%-23%. The results of this study showed that CT 105 disrupts calcium homeostasis and renders neuronal cells more vulnerable to glutamate-induced excitotoxicity, and that some portion of CT 105 has partial beta-sheet conformation in various environments, which may be related to the self-aggregation and toxicity. This may be significantly possibly involved in inducing the neurotoxicity characteristic of AD.

Glutamate and aspartate impair memory retention and damage hypothalamic neurons in adult mice

We examined the effects of systemic administration of monosodium glutamate (MSG) or aspartate (ASP) on the memory retention and neuronal damage in the brains of adult mice. Compared with the control mice, a single intraperitoneal injection of either 4.0 mg/g MSG or 0.5 mg/g ASP after acquisition trial significantly shortened the response latency in the passive avoidance test, accompanying by the transient weight loss. Histopathological analysis of the brains of these mice revealed that neurons in the arcuate nucleus of hypothalamus were damaged markedly by MSG (4.0 mg/g) or ASP (0.5 mg/g). Other brain areas including cerebral cortex and hippocampus did not show any pathological changes. These findings suggest that systemic administration of MSG or ASP could impair memory retention and damage hypothalamic neurons in adult mice.

APP carboxyl-terminal fragment without or with abeta domain equally induces cytotoxicity in differentiated PC12 cells and cortical neurons

Mutations in the beta-amyloid precursor protein (APP) gene cause familial Alzheimer's disease (AD). Although amyloid beta peptide (Abeta) is the principal constituent of senile plaques in AD, other cleavage products of APP are also implicated in playing a role in the pathogenesis of AD. C-terminal fragments of APP (APP-CTs), that contain complete Abeta sequence, are found in neuritic plaques, neurofibrillary tangles and the cytosol of lymphoblastoid cells obtained from AD patients. Our previous report demonstrated that APP-CT105 causes death of differentiated PC12 cells and cultured rat cortical neurons (Kim and Suh [1996] J. Neurochem. 67:1172-1182) and induces strong inward currents in Xenopus oocyte (Fraser et al., [1996] J. Neurochem. 66:2034-2040). In the present study, to investigate which domain of APP-CT105 is responsible for the neurotoxicity, we have made deletion mutants of APP-CT105 without Abeta and transmembrane domain (TM) or without NPTY domain, a putative endocytosis signaling sequence, using the PCR-amplified strategy and the recombinant GST-fusion protein strategy. The effect on cell survival of the deletion mutants of APP-CT105 (8 microM) was then determined by the LDH and MTT assay. We found that C-terminal fragment without NPTY significantly causes cell death in NGF-differentiated PC12 cells and cultured rat cortical neurons. This finding suggests that NPTY may not play an important role in APP-CT105 mediated neurotoxicity. We found, however, that C-terminal fragment without Abeta and TM significantly induces neuronal cell death. Our results suggest that in addition to Abeta, C-terminal fragment of APP without Abeta and TM domain itself may also participate in the neuronal degeneration in AD.

Peptide fragments of beta-amyloid precursor protein: effects on parallel fiber-Purkinje cell synaptic transmission in rat cerebellum

The effects of peptide fragments of the beta-amyloid precursor protein (betaAPP) on parallel fiber (PF)-Purkinje cell synaptic transmission in the rat cerebellum were examined. Transient inward currents associated with calcium influx were induced by localized applications of the 105-amino acid carboxy-terminal fragment (CT105) of betaAPP to discrete dendritic regions of intact Purkinje cells. betaAPP and the amyloid beta (Abeta) peptide fragments Abeta1-16, Abeta25-35, and Abeta1-42 had little or no effect. Inward currents were also observed following applications of CT105 to isolated patches of somatic Purkinje cell membrane. All five proteins/peptides induced some depression of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor-mediated synaptic transmission between PFs and Purkinje cells, through a combination of pre- and postsynaptic effects. CT105 induced the greatest depression, which spread to distant synapses following local application and which was prevented by inhibition of nitric oxide synthase. These data indicate that CT fragments of the betaAPP can modulate AMPA-mediated glutamatergic synaptic transmission in the cerebellar cortex. These fragments may therefore be considered alternative candidates for some of the neurotoxic effects of Alzheimer's disease.

Roles of A beta and carboxyl terminal peptide fragments of amyloid precursor protein in Alzheimer disease

Several lines of evidence indicate that A beta may play an important role in the pathogenesis of AD. However, there are several discrepancies between the production of A beta and the development of the disease. Thus, A beta may not be the sole active fragment of beta-amyloid precursor protein (betaAPP) in the neurotoxicity assiciated with AD. We focused on the amyloidegenic carboxyl terminal fragments of betaAPP containing the full length of A beta (CT105). We synthesized a recombinant carboxyl-terminal 105 amino acid fragment of betaAPP and examined the effects of CT105 and A beta on cultured neurons, Ca++ uptake into rat brain microsomes, Na+-Ca++ exchange activity, ion channel forming activity in lipid bilayers and passive avoidance performance of mice. Our results suggest that the cytotoxic and channel inducing effects of CT105 are much more potent than that of A beta and toxic mechanisms of CT105 are different from those of A beta. Taken together, these lines of evidence postulate that CT is an alternative toxic element important in the generation of the symptoms common to AD.

Dehydroevodiamine.HCl prevents impairment of learning and memory and neuronal loss in rat models of cognitive disturbance

We previously reported that dehydroevodiamine.HCl (DHED) has anticholinesterase and antiamnesic activities. To verify the effects of DHED on cognitive deficits further, we tested it on the scopolamine-induced amnesia model of the rat using the passive avoidance and eight-arm radial maze tests. A single (20 mg/kg p.o.) and repeated (10 mg/kg p.o.) administrations of DHED could significantly reverse the latency time shortened by scopolamine (1 mg/kg i.p.) to control level. The impaired spatial working memory induced by scopolamine (1 mg/kg i.p.) was also improved significantly by a single injection (6.25 mg/kg i.p.) and repeated administrations of DHED (10 mg/kg p.o.) in the eight-arm radial maze test. In addition, we examined the effects of DHED on the memory impairment and the histological changes of the brain after unilateral electrolytic lesion of the entorhinal cortex (EC) and middle cerebral artery occlusion in rats. The cognitive deficits caused by EC lesion and middle cerebral artery occlusion were improved significantly by repeated administrations of DHED (6.25 mg/kg i.p.) after EC lesion or ischemic insult once a day for 7 days in the passive avoidance test. Histological analysis showed that the neuronal loss in the DHED-treated group was notably reduced in the hippocampal area (CA1) of ischemic rats and in the dentate gyrus and hippocampal area (CA1 and CA3) of EC-lesioned rats compared with the nontreated group. The infarction area was decreased significantly by a single administration of DHED (6.25 mg/kg i.p.) 30 min before ischemic insult for 6 h. These results suggest that DHED might be an effective drug for not only the Alzheimer's disease type, but also the vascular type of dementia.

Viral latent membrane protein 1 (LMP-1)-induced CD99 down-regulation in B cells leads to the generation of cells with Hodgkin's and Reed-Sternberg phenotype

Recently we reported that the down-regulation of CD99 (Mic2) is a primary requirement for the generation of Hodgkin's and Reed-Sternberg (H-RS) cells seen in Hodgkin's disease. In this study, we provide evidence that the down-regulation of CD99 is induced by high expression of Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1), which is highly expressed in H-RS cells of EBV-associated Hodgkin's disease. To investigate the effect of LMP-1 on the expression of CD99 in vitro, we established a stable cell line by transfecting an SV40-early promoter driven-LMP-1 expression construct into a neoplastic lymphoblastoid B cell line, IM9, in which the level of endogenous LMP-1 expression is almost negligible. In this cell line, the overexpression of LMP-1 led to the down-regulation of CD99 and the acquisition of morphological and functional characteristics of H-RS cells indistinguishable from those in lymph nodes of Hodgkin's disease patients and in CD99-deficient B cells. In addition, induced LMP-1 expression in an EBV-negative B cell clone, BJAB, directly caused the down-regulation of surface CD99 expression. Northern and Western analysis data, showing that overexpression of LMP-1 negatively influenced the expression of CD99, were supported by experiments in which a CD99 promoter-driven luciferase promoter reporter construct transfected into 293T cells was down-regulated when LMP-1 was coexpressed. Therefore, our data strongly suggest that the EBV LMP-1 protein plays a pivotal role in the down-regulation of CD99 via transcriptional regulation, which leads to the generation of the H-RS cells. (Blood. 2000;95:294-300)

Ultrastructural changes in microvessel with age in the hippocampus of senescence-accelerated mouse (SAM)-P/10

Microvessels in the hippocampus of aged SAM-P/10 (14 months old) showed the following ultrastructural changes compared with those of young-mature controls (3 months old): (1) the majority of capillaries had lost the smooth contours typical of young cases; (2) the luminal surface of capillaries showed irregularity; (3) the endothelial cytoplasm was thicker; (4) vesicles appeared more frequently in the endothelium; (5) interendothelial tight junctions and basement membranes, however, seemed to show no significant abnormalities; (6) pericytes, especially those of arterioles and venules, contained many enlarged cytoplasmic inclusions with honeycomb-like vacuoles; (7) the area of glial perivascular end feet was greater. These morphological findings raise the possibility of impaired blood-brain barrier function and microhemodynamic disturbances in aged SAM-P/10 hippocampus.

Comparison of the structures of beta amyloid peptide (25-35) and substance P in trifluoroethanol/water solution

The three-dimensional structure of beta amyloid peptide (25-35) in aqueous solution with 50% (vol/vol) 2,2,2-trifluoroethanol was determined by NMR spectroscopy. Beta amyloid peptide(Abeta) is the major component of senile plaques found in the brain of patient of Alzheimer's disease. Abeta25-35 is biologically active fragment of Abeta and exhibits some sequence homology with the tachykinin family. In this study, we present the structural similarity between Abeta25-35 and substance P which is a member of tachykinin family in order to examine the possibility of sharing pathways mediated by tachykinin receptors. Both peptides have alpha-helical structures in their C-terminal regions and aromatic rings or hydrophobic side chains in the center of the helix protrude outside. These conformational features are expected to be the key for the interaction with the receptors.

Cation selective channels formed by a C-terminal fragment of beta-amyloid precursor protein

The C-terminal 105 amino acid fragment of beta-amyloid precursor protein (CT105) is highly neurotoxic. To obtain insights into its cytotoxic effect, we examined the ionophoric effects of CT105 (10-1000 nM) on artificial lipid membranes. Macroscopic membrane conductance increased with CT105 concentration and its ionophoric effect was comparable to that of amyloid beta protein. The mean unitary conductance of CT105-induced channels was 120 pS and open-state probability was close to 1 at voltages from -80 to +80 mV. CT105induced channels were selective to cations (PK/ P(Cl) = 10.2), being most selective to Ca2+. These findings suggest that CT105 can cause direct neurotoxic effects by forming Ca2+ permeable cation channels on neuronal membranes.

Negative regulation of gonadotropin-releasing hormone and gonadotropin-releasing hormone receptor gene expression by a gonadotrophin-releasing hormone agonist in the rat hypothalamus

There exists evidence for the presence of ultrashort loop feedback circuits of gonadotropin-releasing hormone (GnRH) secretion in the hypothalamus. It is, however, uncertain whether a similar mechanism is involved in the regulation of GnRH gene expression in vivo. Furthermore, little is known about the regulation of GnRH receptor (GnRHR) expression in the brain. In the present study, we examined the regulation of GnRH and its receptor gene expression by GnRH in vivo. A GnRH agonist, [D-Ala6, des-Gly10]GnRH-ethylamide (des-Gly GnRH), was administered by intracerebroventricular (i.c.v.) injection via the lateral ventricle of ovariectomized and estradiol (OVX + E)-treated rats. The amounts of GnRH and GnRHR mRNA were measured in the preoptic area (POA) and posterior mediobasal hypothalamus (pMBH) micropunch samples from individual rat brain slices by respective competitive reverse transcription-polymerase chain reactions. The i.c.v. administration of des-Gly GnRH significantly decreased GnRH and GnRHR mRNA expression in a dose-and time-related manner: des-Gly GnRH (6 ng) suppressed GnRH and GnRHR mRNA expression within 2 h, and the suppression was maintained without significant variation until 8 h after treatment. Treatment with Antide, [N-Ac-D-Nal(2)1, pCl-D-Phe2, D-Pal(3)3, Lys(Nic)5, D-Lys(Nic)6, Lys(iPR)8, D-Ala10]GnRH (10 ng), a potent GnRH antagonist, did not alter GnRH mRNA expression, but prevented des-Gly GnRH-induced suppression of GnRH mRNA expression. Antide alone decreased GnRHR mRNA expression, but failed to alter agonist-induced suppression of GnRHR mRNA expression. These results demonstrate the existence of an ultrashort loop feedback mechanism for GnRH gene expression in the POA, along with homologous down-regulation of GnRHR mRNA expression in the pMBH.

Inhibition of the NGF and IL-1beta-induced expression of Alzheimer's amyloid precursor protein by antisense oligonucleotides

Alzheimer's disease (AD) is a neurodegenerative disorder of the brain characterized by the extracellular deposition of amyloid in senile plaques and along the walls of the cerebral vasculature. The principal constituent of amyloid deposit is amyloid beta peptide (Abeta) derived from its larger precursor protein, amyloid precursor protein (APP). The overexpression of APP is known to be a risk factor for Abeta deposit in AD and in Down syndrome (DS). The inhibition of APP expression has been thought to be beneficial to patients with AD and DS. In this study, we investigated the effects of antisense oligonucleotide (AO) on the overexpression of APP induced by IL-1beta and NGF. Using phosphorothioate-oligonucleotides against initiation codon significantly reduced the protein levels of APP induced by NGF and IL-1beta to basal level in PC12 cell culture systems. These results showed that these antisense oligonucleotides may have a potential to be a therapeutic agent for some patients with AD and DS.

C-terminal fragment of Alzheimer's amyloid precursor protein inhibits sodium/calcium exchanger activity in SK-N-SH cell

Numerous lines of evidence suggest that some of the neurotoxicity associated with Alzheimer's disease (AD) is due to proteolytic fragments of the amyloid precursor protein (APP). Most research has focused on the amyloid beta peptide (Abeta). However, the possible role of other cleaved products of APP is less clear. We have previously shown that a recombinant carboxy-terminal 105 amino acid fragment (CT 105) of APP induced strong non-selective inward currents and also showed neurotoxicity in PC 12 cells and primary cortical neurons and blocked later phase of long term potentiation (LTP) in rat hippocampus in vivo. In this study, we investigated the effects of CT 105 on Na+-Ca2+ exchanger activity in SK-N-SH human neuroblastoma, in the presence of ouabain and monensin, which are considered to drive Na+-Ca2+ exchanger in the reverse mode. CT 105 inhibited the activity of this exchanger in SK-N-SH cells by approximately 50%.

C-terminal fragment of amyloid precursor protein inhibits calcium uptake into rat brain microsomes by Mg2+-Ca2+ ATPase

Numerous lines of evidence suggest that some of the neurotoxicity associated with Alzheimer's disease (AD) is due to proteolytic fragments of the amyloid precursor protein (APP). Most research has focused on the amyloid beta peptide (A beta). However, the possible role of other cleaved products of APP is less clear. In this study, the effects of a recombinant carboxy terminal 105 amino acid (CT105) fragment of APP on the calcium uptake by endoplasmic reticulum Mg2+-Ca2+ ATPase, the major mechanism for sequestering calcium in this organelle, were investigated. We found that CT 105 is a potent inhibitor of Mg2+-Ca2+ ATPase of endoplasmic reticulum, whereas A beta shows no effect. These results demonstrate that CT 105 inhibits the ability of brain microsomes to sequester calcium and suggest that this inhibitory effect of CT 105 may contribute to disruption of intracellular calcium concentration, possibly being involved in inducing the neural toxicity characteristic of AD.

Catastrophic progression of the disassembly of a modular acetabular component

Disassembly of a metal-backed modular acetabular component used for total hip arthroplasty is becoming more common. If the acetabular disassembly is detected early, the revision procedures are relatively simple. In the case of long-term sustained disassembly, however, there are more complicated problems, and more difficult revision procedures are needed. We report a case of long-term sustained disassembly of a modular acetabular component in order to alert orthopaedic surgeons of the catastrophic progression to more severe complications, such as the loosening of the metal-acetabular component and severe acetabular osteolysis.

Anticholinesterase induces nicotinic receptor modulation

The effects of carbamate anticholinesterases, pyridostigmine and physostigmine, on the function of the nicotinic receptor (nAChR) in TE671 cells was studied, precluding their inhibition of acetylcholine hydrolysis by carbachol usage. In radioassay, the simultaneous application of carbachol and carbamates dose-dependently decreased carbachol-induced 22Na+ influx, compared with carbachol activation alone. Increasing cell preincubation in the presence of carbamates, however, potentiated influx at low concentrations in a time-dependent manner. This facilitating effect of carbamates, even at high concentrations, was significantly increased by washing out these drugs and was blocked by pretreatment with diisopropylfluorophosphate. Similar results were also obtained in whole-cell patch-clamp study. There were insignificant changes in desensitization properties during facilitation. It is thus supposed that facilitation cannot be explained by the inhibition of acetylcholine hydrolysis. These results support a previous hypothesis that acetylcholinesterase might modulate nAChR by an unknown mechanism. In addition, the clinical effects of carbamates may be partly attributed to this facilitation.

Behavioral and neuropathologic changes induced by central injection of carboxyl-terminal fragment of beta-amyloid precursor protein in mice

Expression of the carboxyl-terminal fragment (CT) of the beta-amyloid precursor protein (APP) in transgenic animals has been linked with neurotoxicity. However, it remains to be clarified whether the neurotoxicity is caused by beta-amyloid proteins (A betas) derived from CT or by CT itself. To study the in vivo neurotoxicity of CT, mice were given a single intracerebroventricular injection of a recombinant 105-amino acid CT (CT105; 68.5-685 pmol, intracerebroventricularly), and changes in behavior and in brain histology were examined. Animals given CT105 (410 or 685 pmol, intracerebroventricularly) showed a dose-dependent impairment in the passive avoidance performance, whereas boiled CT105 had no effect. CT105 (685 pmol, intracerebroventricularly) induced reactive gliosis in neocortex and hippocampus and neurodegeneration in neocortex. These results indicate that centrally administered CT105 induces behavioral impairment and neuropathologic changes, suggesting a direct toxic effect of CT105 per se.

The cDNA cloning and ontogeny of mouse alpha-synuclein

Alpha-synuclein has been implicated in the pathogenesis of Parkinson's disease. To investigate the role of alpha-synuclein in the brain, the cDNA clone encoding the mouse cognate of the human alpha-synuclein was isolated from a mouse brain cDNA library. The open reading frame coded for 140 amino acids that share 95% identity with human alpha-synuclein. Northern blot analysis showed that alpha-synuclein mRNA was primarily expressed in brain and spleen of adult mouse. In situ hybridization histochemistry revealed the highest expression of alpha-synuclein mRNA in the hippocampal formation and neocortex of the adult mouse. alpha-Synuclein mRNA expression in the brain was first observed in the hippocampus and neocortex on postnatal day 1. Levels of alpha-synuclein mRNA in these forebrain areas were nearly maximal at postnatal day 7 and remained relatively high until the adult stage. alpha-Synuclein mRNA was expressed in the liver transiently during embryogenesis.

Post-ischemic changes in the expression of Alzheimer's APP isoforms in rat cerebral cortex

A significant porportion (25%) of patients with Alzheimer's disease (AD) also shows vascular pathology. Recent ultrastructural studies demonstrated characteristic and extensive angio-architectural distortions of cerebral capillaries in AD brains. We examined the expression of APP mRNA isoforms of cerebral cortex after transient ischemia by middle cerebral artery occlusion, using RT-PCR. Neuronal damage and glial fibrillary acidic protein immunohistochemistry were also examined histologically. After transient ischemia, the Kunitz protease inhibitor-bearing isoforms (KPI-APP) were increased whereas APP 695, which lacks KPI domain, was decreased. Neuronal damage and GFAP-immunoreactive astrocytes were also observed. These results show that focal, transient ischemia alters KPI-APP/APP 695 ratio in cerebral cortex and this shift in APP isoforms could be related to neurodegeneration and/or activation of astrocytes during the ischemic process.

Cerebral cortical phospholipase A2 activity of senescence-accelerated mouse is increased in an age-dependent manner

The PLA2 activities of both the cytosolic and the membrane fractions from the cerebral cortex of 17-month old senescence-accelerated mouse-prone/10 (SAM-P/10) were significantly increased by 1.3 times compared with those of 2-month old mice. The PLA2 activities were independent of Ca2+ ion and not affected either by dithiothreitol (DTT) or by trifluoromethyl ketone analogs of arachidonic acid (AACOCF3). The PLA2 activities were eluted in a single peak of molecular mass of 170 kDa, using a gel filtration column. These findings suggest that the enhanced PLA2 activity may be related to neuronal degeneration and accelerated senescence of SAM-P/10, and cerebral cortical PLA2 activity categorized as a Ca2+-independent PLA2.

Block of LTP in rat hippocampus in vivo by beta-amyloid precursor protein fragments

The effects of beta-amyloid precursor protein (beta-APP) fragments on plasticity of glutamtatergic synaptic transmission were examined in the hippocampus of urethane anaesthetized rats. I.c.v. injection of beta-amyloid (A beta) 1-40 and 1-42 and the C-terminal fragment CT105 greatly shortened the duration of high frequency stimulation-induced long-term potentiation (LTP) of field excitatory postsynaptic potentials in the CA1 area. Whereas in vehicle injected animals LTP was stable over a 5 h recording period, doses of these peptides (A beta 1-40, 0.4 and 3.5 nmol; A beta1-42, 0.01 nmol; CT105, 0.05 nmol) which did not affect baseline synaptic transmission abolished LTP within 3-5 h. The reduced duration of this form of synaptic plasticity may contribute to the cognitive deficits in Alzheimer's disease.

Enhanced release of secreted form of Alzheimer's amyloid precursor protein from PC12 cells by nicotine

There is mounting evidence indicating that overexpression or aberrant processing of amyloid precursor protein (betaAPP) is causally related to Alzheimer's disease. betaAPP is principally cleaved within the amyloid beta protein domain to release a large soluble ectodomain (betaAPPs) that has been known to have a wide range of trophic and protective functions. Activation of phospholipase C-coupled receptors has been shown to increase the release of betaAPPs through protein kinase C and calcium. Here we have examined whether nicotine can modulate the expression and processing of betaAPP in PC12 cells. Treatment of PC12 cells with nicotine increased the release of a carboxyl-terminally truncated, secreted form of betaAPP into the conditioned medium without affecting the expression level of betaAPP mRNA. The effect of nicotine on the secretion of betaAPPs is concentration (>50 microM)- and time (>2 hr)-dependent and attenuated by cotreatment with either mecamylamine, a specific nicotinic receptor antagonist, or EGTA, a calcium chelator, indicating calcium entry through the neuronal nicotinic acetylcholine receptor is essential in enhanced betaAPPs release by nicotine. However, nicotine did not significantly change the amyloid beta protein secretion from Swedish mutant betaAPP-transfected PC12 cells. These results imply that nicotinic receptor agonist might be beneficial in the treatment of Alzheimer's disease by not only supplementing the deficient cholinergic neurotransmission but also stimulating the release of betaAPPs.

Sphingomyelinase activity is enhanced in cerebral cortex of senescence-accelerated mouse-P/10 with advancing age

The cerebral cortical sphingomyelinase (SMase) activities were detected in the cytosolic and the membrane fractions of cerebral cortex, hippocampus, cerebellum, brainstem, and thalamus/midbrain of senescence-accelerated mouse-prone/10 (SAM-P/10) and SAM-resistant/1 (SAM-R/1) with advancing age, respectively. The SMase activity was increased uniquely in the membrane fraction of the cerebral cortex of SAM-P/10 in an age-dependent manner; The enzyme activities of 10 and 17 months of age were about 25 and 30% higher than those of 2 months of age, respectively. This observation implicates that the membrane-associated SMase activity might be related with accelerated senescence. The cerebral cortical SMase was eluted in a molecular mass of approximately 400 kDa on a gel filtration chromatography and was active in a broad range of pH from 4 to 9. It was also suggested that phosphorylation may be one of the mechanisms regulating the enzyme activity, but not responsible for the increased activity with advancing age.

Lack of interactions between amyloid precursor protein and hydrophilic domains of presenilin 1 and 2 using the yeast two hybrid system

Mutations in the two related genes, presenilin 1 (PS1) and presenilin 2 (PS2), which are predicted multispanning membrane proteins, are responsible for the majority of early-onset familial Alzheimer's disease (FAD). To demonstrate direct interactions between presenilins (PS) and amyloid precursor protein (APP), the authors utilized a yeast two-hybrid system. Various hydrophilic domains derived from PS and those of APP were coexpressed in yeast and tested for the interaction. No detectable interactions were found in any PS/APP set examined. The authors' studies suggest that PS and APP do not interact through their hydrophilic domains in yeast, raising the possibility that interaction may occur indirectly or require proper conformation or subunit formation.

Age-related changes in the expression of Alzheimer's beta APP in the brain of senescence accelerated mouse (SAM)-P/10

Patients with Alzheimer's disease (AD) show loss of memory and cognitive deficits the molecular mechanisms of which are not completely known. We examined age-related changes in the expression levels of beta-amyloid precursor protein (beta APP) in the brain of the senescence accelerated mouse (SAM) P/10, which shows age-dependent brain atrophy and impairment in learning and memory, and in the senescence resistant mouse (SAM)-R/1 using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Levels of both beta APP mRNA and protein increased with age, reaching a peak at 8 months of age in the hippocampus of SAM-P/10. In contrast, beta APP protein level decreased with age in the hippocampus of SAM-R/1 while beta APP mRNA level did not change significantly. Levels of beta APP mRNA and protein showed no change with ageing in other brain regions, including cerebral cortex, thalamus/midbrain and cerebellum brain stem. These results suggest that the beta APP over-expression in the hippocampus might be related to the characteristic memory loss in SAM-P/10.

An etiological role of amyloidogenic carboxyl-terminal fragments of the beta-amyloid precursor protein in Alzheimer's disease

Amyloid beta protein (A beta), 39-43 amino acids long, is the principal constituent of the extracellular amyloid deposits in brain that are characteristic of Alzheimer's disease (AD). Several lines of evidence indicate that A beta may play an important role in the pathogenesis of AD. However, there are several discrepancies between the production of A beta and the development of the disease. Thus, A beta may not be the sole active fragment of beta-amyloid precursor protein (betaAPP) in the neurotoxicity associated with AD. Consequently, the possible effects of other cleaved products of betaAPP need to be explored. The recent concentration on other potentially amyloidogenic products of betaAPP has produced interesting candidates, the most promising of which are the amyloidogenic carboxyl-terminal (CT) fragments of betaAPP. This review discusses a possible etiological role of CT fragments of betaAPP in AD.

In-vivo study on the harmful effect of the extremely low frequency unipolar pulsating magnetic field in mice

We studied the biological effect of a magnetic field on murine brain and kidney. Magnetic field we used was generated by Magno-DR apparatus (Hanil Co., Korea) which produced a high density unipolar square pulsating magnetic field, about 0.3 approximately 0.5 Tesla at 7 Hertz. Animals were placed in the chamber of the machine for various times from 4 hours to 24 hours. Histological sections of brain and kidney were made after perfusion fixation with paraformaldehyde. The light microscopic examination showed eosinophilic change of cytoplasm and positive immunohistochemical reaction to amyloid precursor protein in the neurons of the cerebral cortex. However, the thalamus and brain stem were less affected. The changes in the brain was seen in the mouse exposed more than 12 hours. The renal tubular epithelium showed degenerated tubules scattered in cortical area but little change was noted in glomeruli in the cortex and collecting tubules in the medulla. Immunohistochemistry of the kidney showed weakly positive reaction for the amyloid precursor protein in the distal tubular epithelium after 4 hours of exposure. These data suggest that strong pulsating magnetic fields could induce deleterious effect on the murine brain tissue and renal cortical tubules.

Ionic effects of the Alzheimer's disease beta-amyloid precursor protein and its metabolic fragments

Alzheimer's disease is a progressive dementia characterized in part by deposition of proteinaceous plaques in various areas of the brain. The main plaque protein component is beta-amyloid, a metabolic product of the beta-amyloid precursor protein. Substantial evidence has implicated beta-amyloid (and other amyloidogenic fragments of the precursor protein) with the neurodegeneration observed in Alzheimer's disease. Recently, beta-amyloid precursor protein and its amyloidogenic metabolic fragments have been shown to alter cellular ionic activity, either through interaction with existing channels or by de novo channel formation. Such alteration in ionic homeostasis has also been linked with cellular toxicity and might provide a molecular mechanism underlying the neurodegeneration seen in Alzheimer's disease.

Expression of Alzheimer's amyloid precursor protein in human lymphocyte

Beta-amyloid precursor protein (betaAPP) has been shown to be involved in cell growth regulation. In spleen, the majority of cells showing betaAPP like immunoreactivity was found in the T cell-dependent zone. In Northern blot, the expression of betaAPP was increased to reach the peak at 72 h after the treatment of phytohemagglutinin (PHA). But, in cytofluorometry, almost all CD4(+) T helper/inducer cells and the majority of CD(8+) T suppressor/cytotoxic cells show betaAPP immunoreactivity which remained constant during the stimulation with PHA. These results suggest that betaAPP is a surface molecule of T lymphocyte and the turnover or release of APP might be increased with the treatment of T cell mitogen.

Novel anticholinesterase and antiamnesic activities of dehydroevodiamine, a constituent of Evodia rutaecarpa

To find a new compound with antiamnesic activity, we screened 29 natural products for their abilities to inhibit acetylcholinesterase and reverse scopolamine-induced amnesia. Among the plants tested Evodia rutaecarpa Bentham showed a strong inhibitory effect on acetylcholinesterase in vitro and an anti-amnesic effect in vivo. By sequential fractionation of E. rutaecarpa, the active component was finally identified as dehydroevodiamine hydrochloride (DHED). DHED inhibited acetylcholinesterase activity in a dose-dependent and non-competitive manner. The IC50 value of DHED is 37.8 microM. A single administration of DHED to rats (6.25 mg/kg) significantly reversed the scopolamine-induced memory impairment in a passive avoidance test. The antiamnesic effect of DHED was more potent than that of tacrine which is the only drug for Alzheimer's disease approved by FDA. This potent antiamnesic effect of DHED was thought to be due to the combined effects of acetylcholinesterase inhibition and the known cerebral blood flow enhancement. These results indicate that DHED has novel anti-cholinesterase and antiamnesic activities and might have therapeutic potential in various disorders including Alzheimer's disease.

Limitation of enzyme-conjugated streptavidin-biotin system in the detection of eukaryotic proteins by immunoblot analysis

In a series of Western blot experiments, we discovered that peroxidase-conjugated streptavidin alone without pretreatment of primary and secondary antibodies could react specifically with approximately 145 KD and 75 KD proteins. These bands were eliminated by preincubation with nonconjugated streptavidin. They were found in virtually all tissues of the mouse and rat and various cell lines to a variable degree. It is the thought that these bands may represent some members of biotin-coupled carboxylating enzymes. From these results we suggest that the enzyme-conjugated streptavidin system is not suitable to detect the protein in the eukaryotic cells and tissues by immunoblot analysis, especially those whose size is similar to the biotin-coupled carboxylases.

Neurotoxicity of a carboxyl-terminal fragment of the Alzheimer's amyloid precursor protein

We have previously shown that a recombinant carboxyl-terminal 105-amino-acid fragment (CT105) of the amyloid precursor protein (APP) induced strong non-selective inward currents in Xenopus oocytes. Here we investigated the toxic effect of CT105 peptide on the cultured mammalian cells. The CT105 peptide induced a significant lactate dehydrogenase (LDH) release from cultured rat cortical neurons and PC12 cells in a concentration (from 10 microM)- and time (from 48 h)-dependent manner. The toxic effect of CT105 was more potent than that of any fragments of amyloid beta protein (A beta). However, CT105 peptide did not affect the viability of U251 human glioblastoma cells. In contrast to CT105, A beta increased LDH release only slightly even at 50 microM but significantly inhibited 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction at submicromolar concentrations. Among the various neuroprotective drugs tested, only cholesterol, which alters membrane fluidity, could attenuate the cytotoxicity of CT105 significantly. The CT105 peptide formed multiple self-aggregates on solubilization. Pretreatment with a sublethal concentration of CT105 did not significantly alter the susceptibility of cells to hydrogen peroxide and glutamate. Endogenous CT peptides were found not only in the cell lysates but also in the conditioned medium of PC12 cells. These results imply that CT peptide can directly attack the cell membrane probably by making pores or nonselective ion channels, whereas A beta impairs the intracellular metabolic pathway first. Thus, it is thought that both CT and A beta, which are formed during the processing of APP, may participate in the neuronal degeneration in Alzheimer's disease by different mechanisms.

Amyloidogenic processing of Alzheimer's amyloid precursor protein in vitro and its modulation by metal ions and tacrine

Recent studies implicate that excessive amyloidogenic pathway of amyloid precursor protein (APP) processing may be the final common pathway involved in the pathogensis of AD. In attempts to identify the proteases or factors leading to excessive amyloid deposition, we evaluated the potential role of acethylcholinesterase (AChE) and its associated protease for amyloidogenic processing of APP in vitro. Prolonged incubation of a recombinant APP770 with AChE produced several amyloidogenic fragments accumulating a relatively stable a 18 kDa A beta (amyloid beta-protein) bearing carboxy terminal peptide, which was further degraded by an increased concentration of AChE. Protease inhibitory profiles confirmed the trypsin-like serine protease activity present in AChE preparation. This observed APP processing was significantly enhanced by Ca2+, Mg2+, or Mn2+ at 1 mM concentration and modulated in concentration dependent manners by metal ions such as Ca2+, Zn2+, Fe2+/Fe3+, Al3+, or a tacrine, a centrally active cholinesterase inhibitor. Our data imply that AChE and its associated protease may be involved in the generation a 18 kDa amyloidogenic peptide under certain physiological condition in vivo and that the gradual changes in their proteolytic activities or locations and the locally disturbed metal homeostasis could be factors associated with abnormal accumulation of APP, eventually leading to amyloid deposition in AD brain. In addition, zinc or tacrine treatment of AD patients with high dosage or in the long term may have effects on the process of amyloidogensis.

Molecular physiology, biochemistry, and pharmacology of Alzheimer's amyloid precursor protein (APP)

The function of APP is not yet known in detail but growing evidence exists that APP may mediate cell interactions with the cell surface or soluble glycoproteins and defense mechanisms in the CNS involving the immune system. We describe here the finding that almost all CD4+ lymphocytes and the majority of CD8+ lymphocytes were positive for A beta and the antibodies against A beta or APP did not inhibit the [3H]-thymidine uptake of mitogen-treated lymphocytes significantly. There were no differences in the A beta immunoreactivity on the cell surface of lymphocytes between Alzheimer's disease (AD) and control samples. Excessive amyloidogenic pathway of APP processing may be the final common pathway involved in the pathogenesis of AD. Thus, the identification of proteases or factors leading to aberrant proteolysis which process APP to yield a variety of potentially amyloidogenic fragments would promise pharmacological targets to develop anti-AD drugs. In attempts to define the proteases or factors which alter the balance between nonamyloidogenic and amyloidogenic processing pathways, our study indicates that thrombin or acetylcholinesterase(AChE)-associated protease may be involved in the amyloidogenic processing pathway of APP in vivo to generate amyloidogenic intermediates linked to amyloid deposition. Highly specific and dose-dependent direct modulation of APP processing by biologically available metal ions including Ca2+, Zn2+, Fe2+/Fe3+ and Al3+ suggest the disrupted metal homeostasis as factors leading to overaccumulation of APP and subsequent aberrant proteolysis utilizing excessive amyloidogenic processing pathway. There is mounting evidence that at least some of the neurotoxicity associated with AD is due to fragments from APP. Most research has focused on the toxic effect and the ion channel activity of A beta in causation of the disease. The possible role of other cleaved products of APP is less clear. We investigated the channel-forming ability of various products of APP when applied to Xenopus oocytes and their neurotoxicity in vitro. CT105 peptide was found to be exceedingly potent at 500 nM concentration in forming nonselective ion channels during application from either outside or inside the oocyte and more toxic than either of the A beta fragments, A beta 25-35, or A beta 1-40. Taken together, these results suggest the possible involvement of CT peptide in inducing the neurotoxicity characteristic of AD through the direct damage on the cell membrane. Therefore, we hypothesize that amyloidogenic CT may make nonselective ion channels or pores in the membrane and may cause neuronal death in the early stage of AD and then further metabolized to more stable and less toxic A beta which may be finally deposited in the brain where it could inflict further toxicity to neurons. Here we report successful inhibition of APP gene expression by antisense oligodeoxynucleotides at the mRNA or the protein level in in vitro and cell culture systems.

Membrane currents induced in Xenopus oocytes by the C-terminal fragment of the beta-amyloid precursor protein

There is mounting evidence that at least some of the neurotoxicity associated with Alzheimer's disease (AD) is due to proteolytic fragments of the beta-amyloid precursor protein (beta APP). Most research has focused on the amyloid beta protein (A beta), which has been shown to possess ion channel activity. However, the possible role of other cleaved products of the beta APP is less clear. We have investigated the ability of various products of beta APP to induce membrane ion currents by applying them to Xenopus oocytes, a model system used extensively for investigating electrophysiological aspects of cellular, including neuronal, signalling. We focussed on the 105-amino-acid C-terminal fragment (CT105) (containing the full sequence A beta), which has previously been found to be toxic to cells, although little is known about its mode of action. We have found that CT105 is exceedingly potent, with a threshold concentration of 100-200 nM, in inducing nonselective ion currents when applied from either outside or inside the oocyte and is more effective than either beta APP or the A beta fragments, beta 25-35 or beta 1-40. The ion channel activity of CT105 was concentration dependent and blocked by a monoclonal antibody to A beta. These results suggest the possible involvement of CT105 in inducing the neural toxicity characteristic of AD.

Aggregation of amyloid precursor proteins by aluminum in vitro

The effect of various metal ions on aggregation of human recombinant amyloid precursor protein (APP) in vitro was investigated based on characterizations of altered migration on SDS-PAGE or immunoblots. Most biological metal ions tested had no significant effect on aggregation of APP. In contrast, AlCl3 in particular promoted aggregation of APP or APP-CT105 in a dose dependent manner. This effect of AlCl3 on APP mobility shift was prevented or reversed by the metal chelator, EDTA. Amorphous aggregates were observed in AlCl3 treated APP when examined by EM. These results suggest that aluminum may play a role in the pathogenesis of AD by directly promoting aggregation of APP.

Complete nucleotide sequence and tissue-specific expression of the rat phenylethanolamine N-methyltransferase gene

The rat phenylethanolamine N-methyltransferase (PNMT) gene was isolated from a genomic library by cross-hybridization with a bovine PNMT cDNA probe. Complete nucleotide sequence analysis of a genomic clone showed that this gene contained three exons and spanned about 2.8 kb in length. There were the acute-phase response element, TATA, SP1, and GRE sequences. The physicochemical properties of rat adrenal PNMT were different from those of the brainstem PNMT. However, northern blot and reverse transcription-polymerase chain reaction analysis showed that the rat PNMT gene may not express the multiple forms of mRNA. These results suggest that the rat PNMT gene might produce a single enzyme protein, whose activity may be differentially modulated by tissue-specific environment in the central and peripheral systems.

General pharmacology of cis-malonato[4R,5R)-4,5-bis-(aminomethyl)-2-isopropyl-1,3- dioxolane]platinum(II)

The general pharmacological properties of cis-malonato-[(4R,5R)-4,5- bis(aminomethyl)-2-isopropyl-1.3-dioxolane]platinum(II) (SKI 2053R, CAS 146665-77-2), a new potential anticancer agent, were investigated in mice, rats, guinea pigs, rabbits, cats and dogs. Intravenous administration of SKI 2053R had no effect on the central nervous system. SKI 2053R had no effect on the autonomic nervous system and smooth muscles except that it slightly inhibited the spontaneous motility of isolated rabbit ileum at a concentration of 5 x 10(-5) g/ml. SKI 2053R did not adversely affect the respiratory-cardiovascular system, gastrointestinal system, neuromuscular junction, or renal function. SKI 2053R did not significantly alter the levels of serum glucose, serum free fatty acid and plasma lactate, and did not induce hemolysis. SKI 2053R did not affect blood coagulation mechanism and liver function. SKI 2053R did not exhibit anti-inflammatory activity. It was observed that SKI 2053R increased the formation of hemolytic plaque by spleen cells of sensitized mice at high doses (10 mg/kg and 35 mg/kg). Therefore, it is concluded from these general pharmacological studies that SKI 2053R at the doses showing antitumor activity does not induce severe adverse effects on the central nervous, autonomic nervous, respiratory-cardiovascular, gastrointestinal, peripheral nervous, and other systems in experimental animals.