Decreased hippocampal cholinergic neurostimulating peptide precursor protein associated with stress exposure in rat brain by proteomic analysis

The stress response alters behavior, autonomic function, and secretion of multiple hormones, including corticotropin-releasing factor, adrenocorticotropin hormone, and cortisol, through the hypothalamic-pituitary-adrenal axis. Constitutive stress responses lead to a number of psychiatric disorders, including depression, posttraumatic stress disorder, Alzheimer's disease (AD), and other anxiety disorders through increased stress hormones and other unknown factors. Here, we performed a proteomic analysis of rat brain exposed to restraint stress compared with a nonstress group by using 2D-DIGE and MALDI-TOF analysis. Several proteins were identified by peptide mass fingerprint (PMF), including down-regulated hippocampal cholinergic neurostimulating peptide precursor protein (HCNP-pp). The current study demonstrates that HCNP-pp mRNA and protein expression are decreased in rat hippocampus after stress exposure. The level of HCNP-pp in H19-7, a rat hippocampal cell line, significantly decreases with dexamethasone treatment, a synthetic glucocorticoid. Thus, this finding suggests that HCNP-pp expression may decrease in response to stress exposure. Decreased HCNP-pp from stress exposure may result in lower levels of HCNP that might contribute to a loss of acetylcholine production.     

Brain malformations caused by retroviral vector-mediated gene transfer of hippocampal cholinergic neurostimulating peptide precursor protein into the CNS via embryonic mice ventricles

Hippocampal cholinergic neurostimulating peptide precursor protein (HCNP-pp) is a unique multifunctional protein, being not only the precursor of HCNP, which promotes the phenotype development of septo-hippocampal cholinergic neurons, but also the binding protein of phosphatidylethanolamine, ATP, Raf-1 kinase (known as "Raf-1 kinase inhibitory factor" in peripheral organs), and serine protease. We obtained a high-titer retroviral vector harboring HCNP-pp cDNA by the use of a modified packaging cell line and centrifugation, and by injecting it into embryonic mouse ventricles, we investigated the function of its gene product within the central nervous system (CNS). We found that efficient transduction into hippocampal pyramidal neurons can be achieved by injecting the vector into embryonic brain ventricles on embryonic day 14 (E14). Three days after receiving the intraventricular injection of the high-titer HCNP-pp retrovirus vector on E14, the tissues around the ventricles showed an overexpression of HCNP-pp. This was accompanied by a reduced amount of activated MEK and Erk (as analyzed by histochemical and Western blot methods), suggesting that HCNP-pp also regulates the MAP-kinase cascade within the CNS. Surprisingly, mouse brains that received the HCNP-pp retroviral vector showed massive malformation of the hippocampus and cerebellum when examined 30 days after birth. This shows that strictly regulated HCNP-pp gene expression is necessary for the normal development of the mouse brain, and that the moderate overexpression achieved by retroviral vector-mediated gene transfer is sufficient to cause severe abnormality of entire brain structures.     

High levels of hippocampal cholinergic neurostimulating peptide (HDNP> in the CSF of some patients with Alzhemer's disease

Hippocampal cholinergic neurostimulating peptide (HCNP), originally purified from the hippocampus of young rats, enhances the cholinergic development of rat medial septal nuclei in vitro. This report concerns the determination of the HCNP content of the cerebrospinal fluid (CSF) of 173 clinically, and of 22 clinico-pathologically defined patients. A radiommunossay was used throughout. The HCNP level was relatively uniform among the clinically defind patients for almost all non-Alzheimer's patients, the level fell within the range delimited by ± 2 SD of the mean of all patients taken together, and none of them had a level above this range. By contrast, the early-onset Alzheimer's diseas patients could be divided on the basis of their HCNP level into two groups, one with high levels (markedly above the mean ± 2 SD range), and the other with levels similar to those of the other patients. The analysis of the CSF samples obtained postmortem revealed that Group I Alzheimer-type dementia (ATD) patients with clinico-pathologically established diagnoses had a strikingly higher level of HCNP than patients with either Group II ATD or cerebral vascular diseas. These results suggest that HCNP is involved in certain pathophysiological alterations associated with dementia, and that its determination may be useful in patient evaluation.     

Accumulation of hippocampal cholinergic neurostimulating peptide (HCNP)-related components in Hirano bodies

We have previously isolated from the hippocampus of young rats a novel peptide termed 'hippocampal cholinergic neurostimulating peptide' (HCNP) which specifically enhances the cholinergic activity of the septohippocampal system in vitro . Cloning and base sequence analysis of HCNP-specific cDNA from rat and human cDNA libraries revealed that the 1.1 kDa peptide aligns at the N-terminal region of its 21 kDa precursor protein. An affinity-purified rabbit antibody to rat HCNP prepared by us recognizes the C-terminal domain of the peptide. while an antibody against human HCNP binds to a large portion of the peptide. In this report we show that both antibodies react with HCNP-related components present in the soluble cytosol fraction of human brain tissue.
Immunohistochemical examination of human nervous system tissues from elderly individuals revealed that Hirano bodies in Sommer's sector of the hippocampus were specifically stained by anti-HCNP antibodies. The number of HCNP-positive Hirano bodies was greater in patients with Alzheimer's disease than in normal, age-matched individuals. The immunohistochemical results were substantiated by immunoelectron microscopy. The present findings indicate that HCNP-related components accumulate in Hirano bodies, suggesting that patients who bear these inclusions may have a disturbance of the septohippocampal cholinergic system, considered to be of importance for learning and memory formation.     

盐酸吡格列酮通过提高海马区HCNP含量改善2型糖尿病大鼠学习记忆能力

目的 探讨盐酸吡格列酮通过提高海马区海马胆碱能神经刺激肽(HCNP)含量,对改善2型糖尿病模型大鼠空间记忆能力的作用及其机制. 方法 12周龄雄性SD大鼠按照随机数字表法分为对照组、2型糖尿病组(DM组)、2型糖尿病+盐酸吡格列酮组(DP组),每组12只.对照组大鼠普通饲料喂养,DM组大鼠给予高脂饮食,DP组大鼠高脂饮食20周基础上给予盐酸吡格列酮10 mg/(kg·d)干预8周,每日1次灌胃给药.对照组、DM组同期2mL生理盐水灌胃.采用水迷宫实验检测3组大鼠空间记忆能力;Western blotting法检测3组大鼠海马组织中HNCP前体蛋白(HCNP-pp)含量(以此反映HCNP蛋白含量);逆转录PCR方法检测HCNP-pp、胆碱乙酰基转移酶(CHAT)、1型毒蕈碱样受体(M1R)、α7型烟碱样受体(α7NR)mRNA表达水平. 结果 (1) DM组大鼠逃避潜伏期延长,与对照组、DP组比较差异有统计学意义(P＜0.05).(2)与对照组和DP组相比,DM组大鼠海马HNCP-pp蛋白含量及mRNA相对水平升高,HNCP蛋白含量减少,ChAT、M1R及α7NR mRNA相对含量均下降,差异均有统计学意义(P＜0.05). 结论 盐酸吡咯列酮通过促进HCNP-pp裂解致HCNP增多,进一步作用于相关胆碱能神经受体,以此改善2型糖尿病模型老年大鼠空间记忆能力.     

Distribution of hippocampal cholinergic neurostimulating peptide (HCNP) immunoreactivity in the central nervous system of the rat

Hippocampal cholinergic neurostimulating peptide (HCNP), an undecapeptide isolated from the hippocampal tissue of young rats, enhances the cholinergic development in explant cultures of medial septal nuclei. This report concerns the distribution of HCNP immunoreactivity in the central nervous system (CNS) of 11- and 28-day-old Wistar rats; two affinity-purified anti HCNP antibodies were used. Immunoblot analyses of extracts of different regions of the brain revealed a single 23 kDa band that corresponded to the presumed HCNP precursor protein. Immunostaining of the various CNS structures of the 28-day-old rats was more intense than in those of 11-day-old animals. HCNP immunoreactivity was detected in neurons as well as in glia cells, particularly oligodendroglia. The perikarya of neurons in the cerebral cortex, hippocampus, limbic cortex, caudate, putamen, arcuate nucleus of hypothalamus, trigeminal subnuclei, rostroventrolateral reticular nucleus and dorsal horn of the spinal cord were positively stained. In addition, nerve fibers and terminals in the hypothalamic subnuclei, zona incerta, thalamic subnucleus, caudate, putamen, locus coeruleus, trigeminal subnuclei, dorsal motor nucleus of the vagus, dorsal horn of the spinal cord and intermediolateral column also displayed HCNP immunoreactivity. These observations would suggest that HCNP and its related molecules may have multifunctional roles in the CNS.     

The temporal expression of amyloid precursor protein mRNA in vitro in dissociated hippocampal neuron cultures

The subunit protein of the neurofibrillary tangle, the core protein of the neuritic plaque, and the amyloid of the cerebrovasculature in Alzheimer disease and normal aging is a unique 42-amino acid protein (amyloid beta-protein), suggesting a common origin for these pathological entities. However, the expression of the amyloid precursor protein mRNA (APP mRNA) from which the amyloid beta-protein is derived varies between specific neuronal populations. To determine the conditions under which neuronal synthesis of amyloid beta-protein might contribute to the formation of these structures, we have studied the temporal pattern of APP mRNA expression in developing fetal rabbit hippocampal neurons in vitro. Using in situ hybridization with a biotinylated riboprobe transcribed from a cDNA which includes the region encoding the amyloid beta-protein, we have observed a developmentally specific pattern of APP mRNA hybridization during neuronal maturation in vitro.     

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.     

胶质纤维酸性蛋白在老年痴呆大鼠海马中的表达

为探讨慢性缺血痴呆鼠学习减退与海马内星形胶质细胞表达的关系,基于老年大鼠慢性脑缺血痴呆模型,采用免疫组化技术及迷宫实验,定量分析海马星形胶质细胞变化与学习能力、记忆能力的关系。结果发现,慢性缺血痴呆鼠海马CAl区GFAP阳性细胞数目明显增多,胞体肥大,突起增粗、变长,与对照组相比有显著意义(P<0.05),Y型迷宫测试结果显示,痴呆组大鼠的学习、记忆能力与对照组相比,明显下降。提示海马星形胶质细胞可能参与慢性缺血痴呆大鼠的学习记忆功能。     

Effects of long-term estrogen replacement therapy on beta-amyloid precursor protein and mRNA expression in ovariectomized rat hippocampus

BACKGROUND: In vitro cultures of neural stem cells have shown that estrogen can regulate beta-amyloid precursor protein (β-APP) metabolism and reduce amyloid-beta production.OBJECTIVE: To investigate the effects of long-term oral administration of compound nylestriol or low-dose 17beta-estradiol on β-APP and mRNA expression in the hippocampus of ovariectomized (OVX) rats. DESIGN, TIME AND SETTING: This randomized and controlled experiment was performed at the Animal Laboratory and Laboratory of Endocrine and Metabolic Disease, Xiangya Second Hospital of Central South University between April 2003 and May 2004.MATERIALS: According to body mass, 50 six-month-old female Sprague-Dawley rats were randomly divided into five groups (n = 10 per group): normal control, sham operation, OVX model, 17beta-estradiol (Sigma, USA), and compound nylestriol tablet (Laboratory of Endocrine and Metabolic Disease, Xiangya Second Hospital of Central South University) groups.METHODS: Rats in OVX plus 17beta-estradiol and OVX plus compound nylestriol tablet groups underwent ovariectomy. On the second day after surgery, rats were intragastrically given 17beta-estradiol (100 μg/kg), once per day or compound nylestriol tablet (0.5 mg/kg) and levonorgestrel (0.15 mg/kg) every 2 days.MAIN OUTCOME MEASURES: β-APP expression in the hippocampus of OVX rats was determined using immunohistochemistry (SABC method) and β-APP mRNA expression was analyzed by in situ hybridization. The results were quantitatively analyzed using cell counting and average optical density. RESULTS: The number and optical density of β-APP-positive neurons in every subregion of the hippocampus of OVX rats was dramatically increased compared with normal and sham operation groups following 35 weeks of administration (P < 0.05). Levels of β-APP were decreased following oral administration of compound nylestriol or 17beta-estradiol. In situ hybridization showed that long-term estrogen deficiency and oral administration of compound nylestriol or 17beta-estradiol did not alter the number of β-APP mRNA-positive neurons. CONCLUSION: The results show that long-term estrogen deficiency results in an increase of expression of β-APP though no changes in the expression of β-APP mRNA are detected. Replacement of estrogen with low-dose 17 beta-estradiol or compound nylestriol tablet inhibits the expression of β-APP in the hippocampus to the same extent.     

Decreased glucocorticoid receptor mRNA and dysfunction of HPA axis in rats after removal of the cholinergic innervation to hippocampus

Excess exposure to glucocorticoids can have deleterious effects on physiology and cognition. Glucocorticoids acting via receptors located in hippocampal neurons contribute to negative feedback after stress by terminating the further release of glucocorticoids. The current study investigated the effects of selective immunolesions of septo-hippocampal cholinergic neurons on hippocampal corticosterone receptor mRNA and on hypothalamic-pituitary-adrenal (HPA) activity. As evaluated by in situ hybridization, hippocampal glucocorticoid receptor (GR) mRNA, but not mineralocorticoid receptor (MR) mRNA, was significantly decreased in lesioned rats compared to controls. In a companion study, the peak corticosterone response to one hour of restraint stress did not differ between lesion and control groups but the post-stress decline of corticosterone was more protracted in the lesioned rats. These findings are discussed in terms of their possible relevance to ageing as age-related degeneration of the basal forebrain cholinergic system may contribute to the commonly observed dysfunction of the HPA axis in older animals.     

Nogo-A expression in the human hippocampus in normal aging and in Alzheimer disease

Myelin-associated proteins are involved in the formation and stabilization of myelin sheaths. In addition, they prevent axon regeneration and plasticity in the adult brain. Recent evidence suggests that the expression of certain myelin-associated proteins (e.g. Nogo-A) can be regulated by synaptic activity or by over-expression after neural lesions in brain syndromes such as temporal lobe epilepsy. However, no studies on Alzheimer disease (AD) have been reported in which cell loss and significant synaptic reorganization occurs. In the present study, we analyze in detail the expression of Nogo-A in the hippocampal formation in normal human aging and in AD. Our results indicate that Nogo-A is expressed by oligodendrocytes and neurons in the aged hippocampal formation. In addition, both granule cells and mossy fiber connections are also labeled in the old-aged hippocampi. Interestingly, Nogo-A is over-expressed by hippocampal neurons in AD and is associated with beta-amyloid deposits in senile plaques. Taken together, our results reinforce the hypothesis that Reticulon proteins such as Nogo-A participate in the neuronal responses stemming from hippocampal formation during senescence, and particularly in AD. These findings also indicate that Reticulon proteins could be considered as new putative drug targets in therapies of neurodegenerative disorders.     

Amyloid precursor protein mRNA levels in Alzheimer's disease brain

Insoluble beta-amyloid deposits in Alzheimer's disease (AD) brain are proteolytically derived from the membrane bound amyloid precursor protein (APP). The APP gene is differentially spliced to produce isoforms that can be classified into those containing a Kunitz-type serine protease inhibitor domain (K(+), APP(751), APP(770), APRP(365) and APRP(563)), and those without (K(-), APP(695) and APP(714)). Given the hypothesis that Abeta is a result of aberrant catabolism of APP, differential expression of mRNA isoforms containing protease inhibitors might play an active role in the pathology of AD. We took 513 cerebral cortex samples from 90 AD and 81 control brains and quantified the mRNA isoforms of APP with TaqMan real-time RT-PCR. After adjustment for age at death, brain pH and gender we found a change in the ratio of KPI(+) to KPI(-) mRNA isoforms of APP. Three separate probes, designed to recognise only KPI(+) mRNA species, gave increases of between 28% and 50% in AD brains relative to controls (p=0.002). There was no change in the mRNA levels of KPI-(APP 695) (p=0.898). Therefore, whilst KPI-mRNA levels remained stable the KPI(+) species increased specifically in the AD brains.     

Chronic elevation of amyloid precursor protein in the neocortex or hippocampus of marmosets with selective cholinergic lesions

Summary. In vitro studies have consistently demonstrated a link between cholinergic neurotransmission and amyloid precursor protein metabolism, although few studies have examined such a relationship in vivo and none have been conducted in primate species. The purpose of this study was to test the hypothesis that a reduction in cholinergic activity in neocortical and hippocampal areas consequent upon destruction of ascending cholinergic projections may lead to long-term changes in levels of amyloid precursor protein in these target areas in a primate species. The status of three synaptic proteins associated with neurotransmitter release, synaptophysin, syntaxin and SNAP-25, was also been examined. Selective immunolesions of the basal forebrain cholinergic projections led to increases in amyloid precursor protein-like immunoreactivity in hippocampus and cortex, measured 8 months postlesion. Furthermore, reductions in cortical and hippocampal SNAP-25, but not syntaxin or synaptophysin, immunoreactivity were observed. These results imply that the reduced cholinergic activity characteristic of Alzheimer's disease may contribute to the continuing emergence of neuropathology in addition to the well-known association with cognitive dysfunction. Received September 28, 2000; accepted January 31, 2001     

Neuronal binucleation in Alzheimer disease hippocampus

Aims: The literature and teachings instruct that neurones in the adult brain are fully differentiated, quiescent cells that never divide. Somewhat surprisingly, and counter to such dogma, susceptible neurones in Alzheimer disease display an activated cell cycle phenotype. However, whether this leads to a coordinated procession through the cell cycle is unclear, particularly whether neurones enter anaphase and beyond. To begin to address this issue, in this study we sought to determine whether nuclear division occurs in these neurones. Methods: We examined a series of 101 archived, routinely stained hippocampal sections collected at post mortem for neuropathological evaluation for evidence of neuronal binucleation. Results: We report for the first time, binucleated neurones within the hippocampus in cases of Alzheimer disease but not in control cases ( P  < 0.05). Conclusions: While a relatively rare event, occurring once every 20 000 neurones, this morphological evidence that neuronal cells within the cortical regions of the adult human brain in Alzheimer disease contain two nuclei supports the hypothesis that neuronal cells can re-enter into a coordinated cell cycle that culminates in nuclear division.