Effects of β-amyloid (25–35) on learning in the common snail

The effects of neurotoxic β-amyloid fragment (25–35) on the formation of behavioral sensitization and a conditioned defensive reflex to food were studied. Administration of β-amyloid (25–35) to common snails before the start of training led to a significant reduction in sensitization of the defensive reaction, weakening of the formation of the conditioned defensive reflex to food, and impairment of memory. These impairments to behavioral plasticity may be mediated by changes in synaptic plasticity previously observed in the presence of β-amyloid. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 57, No. 2, pp. 229–236, March–April, 2007.     

Neuroprotective effect of alpha-asarone on spatial memory and nitric oxide levels in rats injected with amyloid-β(25–35)

The chemical α-asarone is an important active substance of the Acori graminei rhizome (AGR). It has pharmacological effects that include antihyperlipidemic, antiinflammatory, and antioxidant activity. Our aim was to study the effects α-asarone on nitric oxide (NO) levels in the hippocampus and temporal cortex of the rat after injection of the fraction 25–35 from amyloid-β (Aβ_(25–35)). In addition we examined the working spatial memory in an eight-arm radial maze. Our results showed a significant increase of nitrites in the hippocampus and temporal cortex of Aβ_(25–35)-treated rats. Other evidence of neuronal damage was the expression of a glial-fibrillar-acid protein and a silver staining. There were impairments in the spatial memory evaluated in the eight-arm radial maze. We wanted to determine whether α-asarone improves the memory correlated with NO overproduction and neuronal damage caused by the injection of Aβ_(25–35) into rats. Then animals received a 16-day treatment of α-asarone before the Aβ_(25–35) injection. Our results show a significant decrease of nitrite levels in the hippocampus and temporal cortex, without astrocytosis and silver-staining cells, which correlates with memory improvement in the α-asarone-treated group. Our results suggest that α-asarone may protect neurons against Aβ_(25–35)–caused neurotoxicity by inhibiting the effects of NO overproduction in the hippocampus and temporal cortex.     

Alteration of the sialylation pattern and memory deficits by injection of Aβ(25-35) into the hippocampus of rats

Previous studies in Parkinson's disease (PD) models suggest that early events along the path to neurodegeneration involve activation of the ubiquitin-proteasome system (UPS), endoplasmic reticulum-associated degradation (ERAD), and the unfolded protein response (UPR) pathways, in both the sporadic and familial forms of the disease, and thus ER stress may be a common feature. Furthermore, impairments in protein degradation have been linked to oxidative stress as well as pathways associated with ER stress. We hypothesize that oxidative stress is a primary initiator in a multi-factorial cascade driving dopaminergic (DA) neurons towards death in the early stages of the disease. We now report results from proteomic analysis of a rotenone-induced oxidative stress model of PD in the human neuroblastoma cell line, SH-SY5Y. Cells were exposed to sub-micromolar concentrations of rotenone for 48h prior to whole cell protein extraction and shotgun proteomic analysis. Evidence for activation of the UPR comes from our observation of up-regulated binding immunoglobulin protein (BiP), heat shock proteins, and foldases. We also observed up-regulation of proteins that contribute to the degradation of misfolded or unfolded proteins controlled by the UPS and ERAD pathways. Activation of the UPR may allow neurons to maintain protein homeostasis in the cytosol and ER despite an increase in reactive oxygen species due to oxidative stress, and activation of the UPS and ERAD may further augment clean-up and quality control in the cell.     

Alteration of the sialylation pattern and memory deficits by injection of Aβ(25–35) into the hippocampus of rats

Sialic acid in glycoconjugates participates in important cellular functions associated with normal development, growth, and communication. Therefore we evaluated the sialylation pattern and memory deficits caused by the injection of Aβ_(25–35) into the hippocampus (Hp) of rats. The eight-arm maze spatial-learning and memory test indicated that the injection of Aβ_(25–35) into subfield CA1 of the Hp impaired both learning and memory. The sialylation pattern was examined using sialic acid-specific lectins. Our results showed that Maackia amurensis agglutinin (MAA, specific for Neu5Acα2,3Gal) showed reactivity in the CA1 and dentate gyrus (DG) subfields of the Hp mainly in the group injected with vehicle, whereas Macrobrachium rosenbergii lectin (MRL, specific for Neu5,9,7Ac) and Sambucus nigra agglutinin (SNA, specific for Neu5Acα2,6Gal-GalNAc) had increased reactivity in the CA1 and DG subfields of the Hp in the Aβ_(25–35)-injected group. The staining pattern of the antibody specific for polysialic acid (a linear homopolymer of α-2,8-linked sialic acid) increased in the CA1 and DG subfields of the Hp of the Aβ_(25–35) group compared to the control group. Our results suggest that injection of Aβ_(25–35) causes impairment in spatial memory and alters the sialylation pattern in response to compensatory reorganization and-or sprouting of dendrites and axons of the surviving neurons.     

Effects of Hericium erinaceus on amyloid β(25-35) peptide-induced learning and memory deficits in mice

The mushroom Hericium erinaceus has been used as a food and herbal medicine since ancient times in East Asia. It has been reported that H. erinaceus promotes nerve growth factor secretion in vitro and in vivo. Nerve growth factor is involved in maintaining and organizing cholinergic neurons in the central nervous system. These findings suggest that H. erinaceus may be appropriate for the prevention or treatment of dementia. In the present study, we examined the effects of H. erinaceus on amyloid β(25-35) peptide-induced learning and memory deficits in mice. Mice were administered 10 μg of amyloid β(25-35) peptide intracerebroventricularly on days 7 and 14, and fed a diet containing H. erinaceus over a 23-d experimental period. Memory and learning function was examined using behavioral pharmacological methods including the Y-maze test and the novel-object recognition test. The results revealed that H. erinaceus prevented impairments of spatial short-term and visual recognition memory induced by amyloid β(25-35) peptide. This finding indicates that H. erinaceus may be useful in the prevention of cognitive dysfunction.     

Temporal changes in myocardial adrenergic regulation with the progression to pump dysfunction after chronic β-adrenoreceptor activation in rats

We evaluated the relationship between myocardial norepinephrine release or inotropic responsiveness to adrenergic stimulation and intrinsic myocardial function after the progression to pump dysfunction induced by chronic β-adrenoreceptor activation (isoproterenol [ISO], 0.1 mg/kg/day for 1 month or 6 months) in rats. Left ventricular (LV) systolic chamber dysfunction occurred after 6 months, but not after 1 month of β-adrenoreceptor activation, as evidenced by reduced LV endocardial fractional shortening determined by echocardiography and a decrease in the slope of the LV systolic pressure–volume relations assessed in isolated, perfused heart preparations. A reduced pump function at 6 months of ISO administration was associated with chamber dilatation, while LV midwall fractional shortening (echocardiography) and the slope of the LV systolic stress–strain relations (isolated heart preparations), indices of intrinsic myocardial function, were unchanged. After 1 month of ISO administration, reduced β₁- and β₂-adrenoreceptor-mediated and sustained α-adrenoreceptor-mediated inotropic responses were noted. Nevertheless, increased inotropic potency of β-adrenoreceptor agonists and upregulation of α-adrenoreceptor-mediated contractile responses were noted after 6 months of ISO administration. Increased adrenergic–inotropic responsiveness after 6 months of ISO administration was associated with depleted LV norepinephrine stores, as evidenced by reduced desipramine-stimulated norepinephrine concentrations in the coronary effluent. In conclusion, in the progression from compensated cardiac hypertrophy to pump dysfunction after chronic sympathetic activation, a preserved intrinsic myocardial contractility is accounted for by paradoxical upregulation of adrenergic-mediated contractile responses.     

Studies of the effects of fragment (25–35) of beta-amyloid peptide on the behavior of rats in a radial maze

Decreases in cognitive functions, particularly long-term (episodic) and working memory, are among the earliest prognostic signs of Alzheimers disease. The toxicity of -amyloid peptide is regarded as a major cause of neurodegeneration and cognitive impairment in this disease. The present report describes studies of the effects of intracerebroventricular administration of -amyloid peptide (25–35) (A(25–35)) on the reproduction of a previously assimilated habit consisting of finding food in an eight-arm radial maze in rats. A (25–35) was given bilaterally at doses of 15 and 30 nmol/animal seven days after preliminary training. Testing was performed 60 days after peptide administration. The results showed that A(25–35) impaired working memory in rats without having any significant effect on the retention of responses. We were unable to demonstrate any relationship between memory impairment and the dose of peptide given. These data provide evidence of the ability of A(25–35) to produce greater degradation of working memory function than long-term memory function.Translated from Zhurnal Vysshei Nervnoi Deyatelnosti, Vol. 54, No. 3, pp. 382–389, May–June, 2004.     

Central Administration of Amyloid β-Peptide (25–35) and Individual Features of Cognitive Behavior in Rats

The individual characteristics of cognitive behavior induced by intracerebroventricular administration of aggregated amyloid β-peptide (25–35) (Aβ_25–35) were studied. A new approach to evaluating individual features of the actions of Aβ_25–35 was used. Navigational training was performed in a single brief session using random target positions, and training sessions were repeated a few days later. These experiments produced the first indication that cognitive behavior was undamaged in 50% of the rats at the early stage of Aβ_25–35 exposure. The activities of the antioxidant enzymes superoxide dismutase and catalase in the cortex and hippocampus were significantly decreased in animals with and without cognitive impairments. We suggest that phenotypic characteristics may underlie the individual features of the animals’ responses to Aβ. At the early stage, aggregated Aβ may induce a compensatory reaction which prevents impairment of cognitive processes.     

Oligomeric and fibrillar species of β-amyloid (Aβ42) both impair mitochondrial function in P301L tau transgenic mice

We recently provided evidence for a mitochondrial dysfunction in P301L tau transgenic mice, a strain modeling the tau pathology of Alzheimer’s disease (AD) and frontotemporal dementia (FTD). In addition to tau aggregates, the AD brain is further characterized by Aβ peptide-containing plaques. When we addressed the role of Aβ, this indicated a synergistic action of tau and Aβ pathology on the mitochondria. In the present study, we compared the toxicity of different Aβ42 conformations in light of recent studies suggesting that oligomeric rather than fibrillar Aβ might be the actual toxic species. Interestingly, both oligomeric and fibrillar, but not disaggregated (mainly monomeric) Aβ42 caused a decreased mitochondrial membrane potential in cortical brain cells obtained from FTD P301L tau transgenic mice. This was not observed with cerebellar preparations indicating selective vulnerability of cortical neurons. Furthermore, we found reductions in state 3 respiration, the respiratory control ratio, and uncoupled respiration when incubating P301L tau mitochondria either with oligomeric or fibrillar preparations of Aβ42. Finally, we found that aging specifically increased the sensitivity of mitochondria to oligomeric Aβ42 damage indicating that oligomeric and fibrillar Aβ42 are both toxic, but exert different degrees of toxicity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Memantine treatment decreases levels of secreted Alzheimer's amyloid precursor protein (APP) and amyloid beta (Aβ) peptide in the human neuroblastoma cells

Memantine, an uncompetitive NMDA receptor antagonist, is a FDA-approved drug used for the treatment of moderate-to-severe Alzheimer's disease (AD). Several studies have documented protective roles of memantine against amyloid beta (Aβ) peptide-mediated damage to neurons in both in vitro and in vivo models. Memantine is also effective in reducing amyloid burden in the brain of APP transgenic mice. However, the exact mechanism by which memantine provides protection against Aβ-mediated neurodegenerative cascade, including APP metabolism, remains to be elucidated. Herein, we investigated the effect of memantine on levels of the secreted form of Aβ precursor protein (APP), secreted Aβ and cell viability markers under short/acute conditions. We treated neuronal SK-N-SH cells with 10 μM memantine and measured levels of secreted total APP (sAPP), APPα isoform and Aβ_(1–40) in a time dependent manner for up to 24 h. Memantine significantly decreased the levels of the secreted form of sAPP, sAPPα and Aβ_(1–40) compared to vehicle treated cells. This change started as early as 8 h and continued for up to 24 h of drug treatment. Unlike sAPP, a slight non-significant increase in total intracellular APP level was observed in 24-h treated memantine cells. Taken together, these results suggest a role for memantine in the transport or trafficking of APP molecules away from the site of their proteolytic cleavage by the secretase enzymes. Such a novel property of memantine warrants further study to define its therapeutic utility.     

Chronic intracerebroventricular exposure to β-amyloid(1–40) impairs object recognition but does not affect spontaneous locomotor activity or sensorimotor gating in the rat

This study examined the cognitive effects of chronic in vivo exposure to beta-amyloid(1-40) via the intracerebroventricular route on two distinct paradigms. The first test evaluated a form of early attentional control referred to as sensorimotor gating in which an antecedent weak prepulse stimulus modulates the reactivity to a subsequent startle-eliciting stimulus. The second test utilized the spontaneous preference for a novel object over that of a familiar one in rats as a measure of object recognition memory. We found that beta-amyloid exposure leads to a severe deficit in the object memory test but spares sensorimotor gating. Moreover, unlike the water maze deficit induced by beta-amyloid (Nag et al., in preparation), the deficit on object recognition was resistant to amelioration by systemic physostigmine treatment at a dose of 0.06 mg/kg per day intraperitoneally. The present results add to previous reports that beta-amyloid exposure can lead to deficits on hippocampal lesion sensitive tasks, suggesting that dysfunction of the rhinal cortices in addition to that of the septohippocampal system is implicated in beta-amyloid-induced behavioral impairments. It therefore lends support to the hypothesis that beta-amyloid exposure can lead to severe impairment across multiple memory systems.     

Phagocytosis and LPS alter the maturation state of β-amyloid precursor protein and induce different Aβ peptide release signatures in human mononuclear phagocytes

Background  

The classic neuritic β-amyloid plaque of Alzheimer's disease (AD) is typically associated with activated microglia and neuroinflammation. Similarly, cerebrovascular β-amyloid (Aβ) deposits are surrounded by perivascular macrophages. Both observations indicate a contribution of the mononuclear phagocyte system to the development of β-amyloid.     

Kihi-to, a herbal traditional medicine, improves Abeta(25–35)-induced memory impairment and losses of neurites and synapses

Background

We previously hypothesized that achievement of recovery of brain function after the injury requires the reconstruction of neuronal networks, including neurite regeneration and synapse reformation. Kihi-to is composed of twelve crude drugs, some of which have already been shown to possess neurite extension properties in our previous studies. The effect of Kihi-to on memory deficit has not been examined. Thus, the goal of the present study is to determine the in vivo and in vitro effects of Kihi-to on memory, neurite growth and synapse reconstruction.

Methods

Effects of Kihi-to, a traditional Japanese-Chinese traditional medicine, on memory deficits and losses of neurites and synapses were examined using Alzheimer's disease model mice. Improvements of Aβ(25–35)-induced neuritic atrophy by Kihi-to and the mechanism were investigated in cultured cortical neurons.

Results

Administration of Kihi-to for consecutive 3 days resulted in marked improvements of Aβ(25–35)-induced impairments in memory acquisition, memory retention, and object recognition memory in mice. Immunohistochemical comparisons suggested that Kihi-to attenuated neuritic, synaptic and myelin losses in the cerebral cortex, hippocampus and striatum. Kihi-to also attenuated the calpain increase in the cerebral cortex and hippocampus. When Kihi-to was added to cells 4 days after Aβ(25–35) treatment, axonal and dendritic outgrowths in cultured cortical neurons were restored as demonstrated by extended lengths of phosphorylated neurofilament-H (P-NF-H) and microtubule-associated protein (MAP)2-positive neurites. Aβ(25–35)-induced cell death in cortical culture was also markedly inhibited by Kihi-to. Since NF-H, MAP2 and myelin basic protein (MBP) are substrates of calpain, and calpain is known to be involved in Aβ-induced axonal atrophy, expression levels of calpain and calpastatin were measured. Treatment with Kihi-to inhibited the Aβ(25–35)-evoked increase in the calpain level and decrease in the calpastatin level. In addition, Kihi-to inhibited Aβ(25–35)-induced calcium entry.

Conclusion

In conclusion Kihi-to clearly improved the memory impairment and losses of neurites and synapses.     

Chronic intracerebroventricular delivery of the secretory phospholipase A2 inhibitor, 12-epi-scalaradial, does not improve outcome after focal cerebral ischemia–reperfusion in rats

Phospholipase A₂s (PLA₂s) seem to be involved in the pathophysiology of ischemic brain injury, but their specific role is far from being completely understood. The present study was carried out to ascertain how and to what extent secretory PLA₂s (sPLA₂s) activity influences outcome after cerebral ischemia–reperfusion, and to correlate this with the inflammatory response. To do this we used the potent and selective sPLA₂ inhibitor, 12-epi-scalaradial. Male Wistar rats were separated into three groups: a control group receiving intracerebroventricular vehicle, and two groups receiving intracerebroventricular 0.005 or 0.5 μg/h 12-epi-scalaradial. Every animal was subjected to middle cerebral artery (MCA) occlusion (90 min, intraluminal thread technique) under continuous monitorization of cerebrocortical perfusion (CP, laser-Doppler flowmetry), followed by reperfusion (3 days). Neurological status, infarct volume, and myeloperoxidase (MPO) activity were the main end points. Three days after the 90-min ischemia period, neurological examination did not reveal significant differences between the three groups of rats. Control rats showed a mean infarct volume of 145.9 ± 24.7 mm³ (21 ± 4.1% of the ipsilateral hemisphere volume), while mean infarct volume in rats treated with 0.005 or 0.5 μg/h 12-epi-scalaradial increased to 164.8 ± 86.8 mm³ (22.0 ± 10.9%) and 211.5 ± 12.2 mm³ (28 ± 3%, P < 0.05), respectively. Treatment with the highest dose of 12-epi-scalaradial (0.5 μg/h) increased MPO activity in the ipsilateral hemisphere by about 140% (from 0.59 ± 0.59 to 1.42 ± 1.03 units of activity/g of tissue in comparison with the control ischemic hemisphere, P < 0.05). Overall, our results point to a positive rather than a negative influence of sPLA₂ activity during ischemia. This, along with its inability to decrease the inflammatory response, does not allow to propose the use of 12-epi-scalardial as a potential drug for stroke therapy.     

Changes in Cell Proliferation in the Subventricular Zone of the Brain in Adult Rats Given β-Amyloid Peptide (25–35)

The effects of intracerebroventricular administration of fragment (25–35) of β-amyloid peptide [Aβ(25–35)] on cell proliferation in the subventricular zone of the dentate gyrus of the hippocampus in adult rats were analyzed. Animals received doses of 15 nmol of pre-aggregated Aβ(25–35) or the Aβ(35–25) control peptide, or solvent (sterile water) into the lateral ventricles. On post-injection days 1–5, rats received intraperitoneal injections of the thymidine analog 5-bromo-2’-deoxyuridine (BrdU). BrdU incorporated into DNA was detected immunohistochemically on frontal brain sections six and 12 days after peptide administration. At six days, the numbers of BrdU-containing cells in the subventricular zone showed no differences between the study groups. At 12 days, the total number of BrdU-positive cells decreased significantly in all study groups. At the same time, the number of labeled cells in rats given Aβ(25–35) was significantly greater in this brain zone than in animals given water or the control peptide. Thus, Aβ(25–35) significantly increased cell proliferation in the subventricular zone after intracerebroventricular administration.     

A comparison of efficacy and safety of 2-year telbivudine and entecavir treatment in patients with chronic hepatitis B: a match–control study

There are limited data comparing the clinical outcomes between telbivudine and entecavir. We consecutively enrolled 115 telbivudine-naive and 115 entecavir-naive chronic hepatitis B patients, who were matched for age, sex, hepatitis B e antigen (HBeAg) status and cirrhosis, and treated for at least 2 years or less than 2 years but had developed resistance. Except for the rate of HBeAg seroconversion, which was similar, patients in the entecavir group had better clinical outcomes than those in the telbivudine group for alanine aminotransferase normalization (85.2% vs 78.4%, p <0.048), undetectable HBV DNA (96.5% vs 74.8%, p <0.001), and viral resistance (0.9% vs 21.7%, p <0.001) after 2 years of treatment, After applying roadmap or super-responders concepts, entecavir still had better outcomes than telbivudine in undetectable HBV DNA and viral resistance. The cumulative incidence of hepatocellular carcinoma development was similar between telbivudine-naive and entecavir-naive patients (p 0.565). In renal function analysis, there were significantly more patients with estimated glomerular filtration rate (eGFR) category improvement in both the telbivudine and entecavir groups at year 1 (p 0.006 and p 0.047, respectively). The rate of virological improvement was significantly higher with entecavir than with telbivudine after 2 years of treatment, whether applying the concepts of roadmap or super-responders. The incidence of hepatocellular carcinoma was similar between telbivudine and entecavir. Both telbivudine and entecavir were associated with eGFR improvement, especially in patients with renal insufficiency.     

Effects of 17β-estradiol and its isomer 17α-estradiol on learning in rats with chronic cholinergic deficiency in the brain

It was shown for the first time that estrogens 17β- and 17α-estradiols compensate impaired cognitive functions in rats with partial chronic deprivation of cholinergic functions in the central nervous system induced by intracerebral administration of selective cholinergic neurotoxin AF64A. 17β-Estradiol produced strong dose-dependent changes in the weights of hormone-sensitive endocrine glands, while 17α-estradiol did not affect the weight of the gonads and slightly influenced (in high concentration) the weights of the adrenal glands and thymus. The positive effects of exogenous 17β- and 17α-estradiols on cognitive functions are due to their antioxidant properties, rather than due to specific action on hormone-sensitive endocrine glands. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 5, pp. 525–527, May, 2000     

Critical role of cPLA(2) in Aβ oligomer-induced neurodegeneration and memory deficit

Soluble beta-amyloid (Aβ) oligomers are considered to putatively play a critical role in the early synapse loss and cognitive impairment observed in Alzheimer's disease. We previously demonstrated that Aβ oligomers activate cytosolic phospholipase A(2) (cPLA(2)), which specifically releases arachidonic acid from membrane phospholipids. We here observed that cPLA(2) gene inactivation prevented the alterations of cognitive abilities and the reduction of hippocampal synaptic markers levels noticed upon a single intracerebroventricular injection of Aβ oligomers in wild type mice. We further demonstrated that the Aβ oligomer-induced sphingomyelinase activation was suppressed and that phosphorylation of Akt/protein kinase B (PKB) was preserved in neuronal cells isolated from cPLA(2)(-/-) mice. Interestingly, expression of the Aβ precursor protein (APP) was reduced in hippocampus homogenates and neuronal cells from cPLA(2)(-/-) mice, but the relationship with the resistance of these mice to the Aβ oligomer toxicity requires further investigation. These results therefore show that cPLA(2) plays a key role in the Aβ oligomer-associated neurodegeneration, and as such represents a potential therapeutic target for the treatment of Alzheimer's disease.     

Changes in AMPA subunit expression in the mouse brain after chronic treatment with the antidepressant maprotiline: a link between noradrenergic and glutamatergic function?

Potentiation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor function has been proposed as being useful in the treatment of depression, but thus far, little is known about the possible changes in AMPA receptor expression in the brain, after antidepressant treatment. The present study was carried out to study the expression of AMPA receptor subunits in different brain regions of mice that had been chronically injected with maprotiline. The latter is a modified tricyclic antidepressant that functions as a noradrenaline uptake inhibitor. Daily intraperitoneal injection with 10 mg/kg maprotiline for 30 days resulted in significantly increased GluR1 and GluR2/3 subunit expression in the nucleus accumbens and dorsal striatum as detected by immunohistochemistry; and significantly increased GluR1 and GluR2/3 expression in the hippocampus, as demonstrated by Western blot analysis. No change, or a decrease in GluR2 expression was detected in all the brain regions by both immunohistochemistry and Western blots. The increase in GluR1 and GluR2/3, but no increase in GluR2 subunits suggests that there could be an increase in calcium permeability of AMPA receptors in limbic/striatal brain regions after maprotiline treatment. This could lead to increased synaptic activity or plasticity in the hippocampus and striatum, and may underlie the therapeutic effect of maprotline, and possibly, other antidepressant drugs.