Neuropeptide Y immunoreactivity is reduced in cerebral cortex in Alzheimer's disease

Neprilysin inhibitors and risk of Alzheimer's disease: A future perspective

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disease with multifaceted neuropathological disorders. AD is characterized by intracellular accumulation of phosphorylated tau proteins and extracellular deposition of amyloid beta (Aβ). Various protease enzymes, including neprilysin (NEP), are concerned with the degradation and clearance of Aβ. Indeed, a defective neuronal clearance pathway due to the dysfunction of degradation enzymes might be a possible mechanism for the accumulation of Aβ and subsequent progression of AD neuropathology. NEP is one of the most imperative metalloproteinase enzymes involved in the clearance of Aβ. This review aimed to highlight the possible role of NEP inhibitors in AD. The combination of sacubitril and valsartan which is called angiotensin receptor blocker and NEP inhibitor (ARNI) may produce beneficial and deleterious effects on AD neuropathology. NEP inhibitors might increase the risk of AD by the inhibition of Aβ clearance, and increase brain bradykinin (BK) and natriuretic peptides (NPs), which augment the pathogenesis of AD. These verdicts come from animal model studies, though they may not be applied to humans. However, clinical studies revealed promising safety findings regarding the use of ARNI. Moreover, NEP inhibition increases various neuroprotective peptides involved in inflammation, glucose homeostasis and nerve conduction. Also, NEP inhibitors may inhibit dipeptidyl peptidase 4 (DPP4) expression, ameliorating insulin and glucagon-like peptide 1 (GLP-1) levels. These findings proposed that NEP inhibitors may have a protective effect against AD development by increasing GLP-1, neuropeptide Y (NPY) and substance P, and deleterious effects by increasing brain BK. Preclinical and clinical studies are recommended in this regard.

Cross talk about the role of Neuropeptide Y in CNS disorders and diseases

A peptide composed of a 36 amino acid called Neuropeptide Y (NPY) is employed in a variety of physiological processes to manage and treat conditions affecting the endocrine, circulatory, respiratory, digestive, and neurological systems. NPY naturally binds to G-protein coupled receptors, activating the Y-receptors (Y1-Y5 and y6). The findings on numerous therapeutic applications of NPY for CNS disease are presented in this review by the authors. New targets for treating diseases will be revealed by medication combinations that target NPY and its receptors. This review is mainly focused on disorders such as anxiety, Alzheimer's disease, Parkinson's disease, Huntington's disease, Machado Joseph disease, multiple sclerosis, schizophrenia, depression, migraine, alcohol use disorder, and substance use disorder. The findings from the preclinical studies and clinical studies covered in this article may help create efficient therapeutic plans to treat neurological conditions on the one hand and psychiatric disorders on the other. They may also open the door to the creation of novel NPY receptor ligands as medications to treat these conditions.

Serum tau protein elevation in migraine: a cross-sectional case-control study

BACKGROUND

Migraine is a disorder associated with neuropeptide release, pain and inflammation. Tau protein has recently been linked to inflammatory diseases and can be influenced by neuropeptides such as CGRP, a key neurotransmitter in migraine. Here, we report serum concentrations of total-tau protein in migraine patients and healthy controls.

METHODS

In this cross-sectional study, interictal blood samples from n = 92 patients with episodic migraine (EM), n = 93 patients with chronic migraine (CM), and n = 42 healthy matched controls (HC) were studied. We assessed serum total-tau protein (t-tau) and for comparison neurofilament light chain protein (NfL), glial fibrillary acidic protein (GFAP), and ubiquitin carboxy-terminal hydrolase L (UCH-L1) concentrations using the Neurology 4-plex kit, on a single molecule array HD-X Analyzer (Quanterix Corp Lexington, MA). Matched serum/cerebrospinal fluid (CSF) samples were used for post-hoc evaluations of a central nervous system (CNS) source of relevant findings. We applied non-parametric tests to compare groups and assess correlations.

RESULTS

Serum t-tau concentrations were elevated in EM [0.320 (0.204 to 0.466) pg/mL] and CM [0.304 (0.158 to 0.406) pg/mL] patients compared to HC [0.200 (0.114 to 0.288) pg/mL] (p = 0.002 vs. EM; p = 0.025 vs. CM). EM with aura [0.291 (0.184 to 0.486 pg/mL); p = 0.013] and EM without aura [0.332 (0.234 to 0.449) pg/mL; p = 0.008] patients had higher t-tau levels than HC but did not differ between each other. Subgroup analysis of CM with/without preventive treatment revealed elevated t-tau levels compared to HC only in the non-prevention group [0.322 (0.181 to 0.463) pg/mL; p = 0.009]. T-tau was elevated in serum (p = 0.028) but not in cerebrospinal fluid (p = 0.760). In contrast to t-tau, all proteins associated with cell damage (NfL, GFAP, and UCH-L1), did not differ between groups.

DISCUSSION

Migraine is associated with t-tau elevation in serum but not in the CSF. Our clinical study identifies t-tau as a new target for migraine research.

Exploring the Therapeutic Effect of Neurotrophins and Neuropeptides in Neurodegenerative Diseases: at a Glance

Neurotrophins and neuropeptides are the essential regulators of peripheral nociceptive nerves that help to induce, sensitize, and maintain pain. Neuropeptide has a neuroprotective impact as it increases trophic support, regulates calcium homeostasis, and reduces excitotoxicity and neuroinflammation. In contrast, neurotrophins target neurons afflicted by ischemia, epilepsy, depression, and eating disorders, among other neuropsychiatric conditions. Neurotrophins are reported to inhibit neuronal death. Strategies maintained for "brain-derived neurotrophic factor (BDNF) therapies" are to upregulate BDNF levels using the delivery of protein and genes or compounds that target BDNF production and boosting BDNF signals by expanding with BDNF mimetics. This review discusses the mechanisms of neurotrophins and neuropeptides against acute neural damage as well as highlighting neuropeptides as a potential therapeutic agent against Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), and Machado-Joseph disease (MJD), the signaling pathways affected by neurotrophins and their receptors in both standard and diseased CNS systems, and future perspectives that can lead to the potent application of neurotrophins and neuropeptides in neurodegenerative diseases (NDs).

Alternative Pharmacological Strategies for the Treatment of Alzheimer's Disease: Focus on Neuromodulator Function

Alzheimer's disease (AD) is a neurodegenerative disorder, comprising 70% of dementia diagnoses worldwide and affecting 1 in 9 people over the age of 65. However, the majority of its treatments, which predominantly target the cholinergic system, remain insufficient at reversing pathology and act simply to slow the inevitable progression of the disease. The most recent neurotransmitter-targeting drug for AD was approved in 2003, strongly suggesting that targeting neurotransmitter systems alone is unlikely to be sufficient, and that research into alternate treatment avenues is urgently required. Neuromodulators are substances released by neurons which influence neurotransmitter release and signal transmission across synapses. Neuromodulators including neuropeptides, hormones, neurotrophins, ATP and metal ions display altered function in AD, which underlies aberrant neuronal activity and pathology. However, research into how the manipulation of neuromodulators may be useful in the treatment of AD is relatively understudied. Combining neuromodulator targeting with more novel methods of drug delivery, such as the use of multi-targeted directed ligands, combinatorial drugs and encapsulated nanoparticle delivery systems, may help to overcome limitations of conventional treatments. These include difficulty crossing the blood-brain-barrier and the exertion of effects on a single target only. This review aims to highlight the ways in which neuromodulator functions are altered in AD and investigate how future therapies targeting such substances, which act upstream to classical neurotransmitter systems, may be of potential therapeutic benefit in the sustained search for more effective treatments.

Whole Blood Transcriptome Characterization of 3xTg-AD Mouse and Its Modulation by Transcranial Direct Current Stimulation (tDCS)

The 3xTg-AD mouse is a widely used model in the study of Alzheimer’s Disease (AD). It has been extensively characterized from both the anatomical and behavioral point of view, but poorly studied at the transcriptomic level. For the first time, we characterize the whole blood transcriptome of the 3xTg-AD mouse at three and six months of age and evaluate how its gene expression is modulated by transcranial direct current stimulation (tDCS). RNA-seq analysis revealed 183 differentially expressed genes (DEGs) that represent a direct signature of the genetic background of the mouse. Moreover, in the 6-month-old 3xTg-AD mice, we observed a high number of DEGs that could represent good peripheral biomarkers of AD symptomatology onset. Finally, tDCS was associated with gene expression changes in the 3xTg-AD, but not in the control mice. In conclusion, this study provides an in-depth molecular characterization of the 3xTg-AD mouse and suggests that blood gene expression can be used to identify new biomarkers of AD progression and treatment effects.

Neuropathology of the Brainstem to Mechanistically Understand and to Treat Alzheimer's Disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder as yet without effective therapy. Symptoms of this disorder typically reflect cortical malfunction with local neurohistopathology, which biased investigators to search for focal triggers and molecular mechanisms. Cortex, however, receives massive afferents from caudal brain structures, which do not only convey specific information but powerfully tune ensemble activity. Moreover, there is evidence that the start of AD is subcortical. The brainstem harbors monoamine systems, which establish a dense innervation in both allo- and neocortex. Monoaminergic synapses can co-release neuropeptides either by precisely terminating on cortical neurons or, when being “en passant”, can instigate local volume transmission. Especially due to its early damage, malfunction of the ascending monoaminergic system emerges as an early sign and possible trigger of AD. This review summarizes the involvement and cascaded impairment of brainstem monoaminergic neurons in AD and discusses cellular mechanisms that lead to their dysfunction. We highlight the significance and therapeutic challenges of transmitter co-release in ascending activating system, describe the role and changes of local connections and distant afferents of brainstem nuclei in AD, and summon the rapidly increasing diagnostic window during the last few years.

Trait anxiety, a personality risk factor associated with Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease in elderly population and the leading cause of dementia worldwide. While senile plaques and neurofibrillary tangles have been proposed as the principal histopathologic hallmarks of AD, the exact etiology of this disease is still far from being clearly understood. AD has been recognized as pathological consequences of complex interactions among genetic, aging, medical, life style and psychosocial factors. Recently, the roles of neuroticism personality traits in AD incidence and progression have come into focus. More specifically, increasing evidence has further shown that the trait anxiety, one major component of neuroticism predicting the individual vulnerability in response to stress, is a risk factor for AD and may correlated with various AD pathologies. In this review, we summarized recent literature on the association of trait anxiety with AD. We also discussed the possible neuroendocrinological and neurochemical mechanisms of this association, which may provide clinical implications for AD diagnosis and therapy.

Assessments of the Effect of Neurokinin B on Toxic Aβ Aggregates in Alzheimer's Disease with the Molecular Mechanisms' Action

Clinical trials of past and current treatments for Alzheimer's disease (AD) patients on the market suffer from the dual drawbacks of a lack of efficacy and side effects. Neuropeptides have been highlighted by their potential to protect cells against AD and can reverse the toxic effect induced by Aβ in cultured neurons. One of the neuropeptides that has insufficient attention in the literature as a potential treatment for prevention of the progression of AD is neurokinin B (NKB). There are critical and unresolved questions concerning the activation, and the molecular mechanisms underlying NKB effect on prevention of Aβ aggregation remain unknown. The current work identifies for the first time the specific interactions that contribute to the inhibition and prevention of initial seeding of polymorphic early-stage dimers. Three main conclusions are observed in this work. First, NKB inhibits formation of polymorphic early-stage fibrillar Aβ dimers. The efficiency of the inhibition depends on the concentration of NKB (i.e., NKB:Aβ ratio). Second, NKB has an excellent effect of preventing the formation of initial seeding of early-stage nonfibrillar Aβ dimers. Third, NKB peptides may self-assemble to form cross-α fibril-like structure during the inhibition activity of the polymorphic early-stage fibrillar Aβ dimers but not during the prevention activity of early-stage nonfibrillar Aβ dimers. The work provides crucial information for future experimental studies to approve the functional effect of NKB on inhibition and prevention of Aβ polymorphic early-stage oligomers.

Roles of Neuropeptide Y in Neurodegenerative and Neuroimmune Diseases

Neuropeptide Y (NPY) is a neurotransmitter or neuromodulator that mainly exists in the nervous system. It plays a neuroprotective role in organisms and widely participates in the regulation of various physiological processes in vivo. Studies in both humans and animal models have been revealed that NPY levels are altered in some neurodegenerative and neuroimmune disorders. NPY plays various roles in these diseases, such as exerting a neuroprotective effect, increasing trophic support, decreasing excitotoxicity, regulating calcium homeostasis, and attenuating neuroinflammation. In this review, we will focus on the roles of NPY in the pathological mechanisms of neurodegenerative and neuroimmune diseases, highlighting NPY as a potential therapeutic target in these diseases.

Synaptic plasticity modulation by circulating peptides and metaplasticity: Involvement in Alzheimer's disease

Synaptic plasticity is a cellular process involved in learning and memory whose alteration in its two main forms (Long Term Depression (LTD) and Long Term Potentiation (LTP)), is observed in most brain pathologies, including neurodegenerative disorders such as Alzheimer's disease (AD). In humans, AD is associated at the cellular level with neuropathological lesions composed of extracellular deposits of β-amyloid (Aβ) protein aggregates and intracellular neurofibrillary tangles, cellular loss, neuroinflammation and a general brain homeostasis dysregulation. Thus, a dramatic synaptic environment perturbation is observed in AD patients, involving changes in brain neuropeptides, cytokines, growth factors or chemokines concentration and diffusion. Studies performed in animal models demonstrate that these circulating peptides strongly affect synaptic functions and in particular synaptic plasticity. Besides this neuromodulatory action of circulating peptides, other synaptic plasticity regulation mechanisms such as metaplasticity are altered in AD animal models. Here, we will review new insights into the study of synaptic plasticity regulatory/modulatory mechanisms which could influence the process of synaptic plasticity in the context of AD with a particular attention to the role of metaplasticity and peptide dependent neuromodulation.

Neuropeptide Y (NPY) as a therapeutic target for neurodegenerative diseases

Neuropeptide Y (NPY) and NPY receptors are widely expressed in the mammalian central nervous system. Studies in both humans and rodent models revealed that brain NPY levels are altered in some neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and Machado-Joseph disease. In this review, we will focus on the roles of NPY in the pathological mechanisms of these disorders, highlighting NPY as a neuroprotective agent, as a neural stem cell proliferative agent, as an agent that increases trophic support, as a stimulator of autophagy and as an inhibitor of excitotoxicity and neuroinflammation. Moreover, the effect of NPY in some clinical manifestations commonly observed in Alzheimer's disease, Parkinson's disease, Huntington's disease and Machado-Joseph disease, such as depressive symptoms and body weight loss, are also discussed. In conclusion, this review highlights NPY system as a potential therapeutic target in neurodegenerative diseases.

Systemic Central Nervous System (CNS)-targeted Delivery of Neuropeptide Y (NPY) Reduces Neurodegeneration and Increases Neural Precursor Cell Proliferation in a Mouse Model of Alzheimer Disease

Neuropeptide Y (NPY) is one of the most abundant protein transmitters in the central nervous system with roles in a variety of biological functions including: food intake, cardiovascular regulation, cognition, seizure activity, circadian rhythms, and neurogenesis. Reduced NPY and NPY receptor expression is associated with numerous neurodegenerative disorders including Alzheimer disease (AD). To determine whether replacement of NPY could ameliorate some of the neurodegenerative and behavioral pathology associated with AD, we generated a lentiviral vector expressing NPY fused to a brain transport peptide (apoB) for widespread CNS delivery in an APP-transgenic (tg) mouse model of AD. The recombinant NPY-apoB effectively reversed neurodegenerative pathology and behavioral deficits although it had no effect on accumulation of Aβ. The subgranular zone of the hippocampus showed a significant increase in proliferation of neural precursor cells without further differentiation into neurons. The neuroprotective and neurogenic effects of NPY-apoB appeared to involve signaling via ERK and Akt through the NPY R1 and NPY R2 receptors. Thus, widespread CNS-targeted delivery of NPY appears to be effective at reversing the neuronal and glial pathology associated with Aβ accumulation while also increasing NPC proliferation. Overall, increased delivery of NPY to the CNS for AD might be an effective therapy especially if combined with an anti-Aβ therapeutic.

Transgenic mice overexpressing amyloid precursor protein exhibit early metabolic deficits and a pathologically low leptin state associated with hypothalamic dysfunction in arcuate neuropeptide Y neurons

Weight loss is a prominent early feature of Alzheimer's disease (AD) that often precedes the cognitive decline and clinical diagnosis. While the exact pathogenesis of AD remains unclear, accumulation of amyloid-β (Aβ) derived from the amyloid precursor protein (APP) in the brain is thought to lead to the neuronal dysfunction and death underlying the dementia. In this study, we examined whether transgenic mice overexpressing the Swedish mutation of APP (Tg2576), recapitulating selected features of AD, have hypothalamic leptin signaling dysfunction leading to early body weight deficits. We found that 3-month-old Tg2576 mice, before amyloid plaque formation, exhibit decreased weight with markedly decreased adiposity, low plasma leptin levels, and increased energy expenditure without alterations in feeding behavior. The expression of the orexigenic neuropeptide Y (NPY) in the hypothalamus to the low leptin state was abnormal at basal and fasting conditions. In addition, arcuate NPY neurons exhibited abnormal electrophysiological responses to leptin in Tg2576 hypothalamic slices or wild-type slices treated with Aβ. Finally, the metabolic deficits worsened as Tg2576 mice aged and amyloid burden increased in the brain. These results indicate that excess Aβ can potentially disrupt hypothalamic arcuate NPY neurons leading to weight loss and a pathologically low leptin state early in the disease process that progressively worsens as the amyloid burden increases. Collectively, these findings suggest that weight loss is an intrinsic pathological feature of Aβ accumulation and identify hypothalamic leptin signaling as a previously unrecognized pathogenic site of action for Aβ.

The effect of neuropeptide Y on cell survival and neurotrophin expression in in-vitro models of Alzheimer's disease

Alzheimer's disease (AD) is a disorder characterized by the accumulation of abnormally folded protein fragments in neurons, i.e., β-amyloid (Aβ) and tau protein, leading to cell death. Several neuropeptides present in the central nervous system (CNS) are believed to be involved in the pathophysiology of AD. Among them, neuropeptide Y (NPY), a small peptide widely distributed throughout the brain, has generated interest because of its role in neuroprotection against excitotoxicity in animal models of AD. In addition, it has been shown that NPY modulates neurogenesis. Interestingly, these latter effects are similar to those elicited by neurotrophins, which are critical molecules for the function and survival of neurons that degenerate during the course of AD. In this review we summarize the evidence for the involvement of NPY and neurotrophins in AD pathogenesis, and the similarity between them in CNS neurons. Finally, we recapitulate our recent in-vitro evidence for the involvement of neurotrophin nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in the neuroprotective effect elicited by NPY in AD neuron-like models (neuroblastoma cells or primary cultures exposed to toxic concentrations of Aβ's pathogenic fragment 25-35), and propose a putative mechanism based on NPY-induced inhibition of voltage-dependent Ca(2+) influx in pre- and post-synaptic neurons.

Humans and great apes share increased neocortical neuropeptide Y innervation compared to other haplorhine primates

Neuropeptide Y (NPY) plays a role in a variety of basic physiological functions and has also been implicated in regulating cognition, including learning and memory. A decrease in neocortical NPY has been reported for Alzheimer's disease, schizophrenia, bipolar disorder, and depression, potentially contributing to associated cognitive deficits. The goal of the present analysis was to examine variation in neocortical NPY-immunoreactive axon and varicosity density among haplorhine primates (monkeys, apes, and humans). Stereologic methods were used to measure the ratios of NPY-expressing axon length density to total neuron density (ALv/Nv) and NPY-immunoreactive varicosity density to neuron density (Vv/Nv), as well as the mean varicosity spacing in neocortical areas 10, 24, 44, and 22 (Tpt) of humans, African great apes, New World monkeys, and Old World monkeys. Humans and great apes showed increased cortical NPY innervation relative to monkey species for ALv/Nv and Vv/Nv. Furthermore, humans and great apes displayed a conserved pattern of varicosity spacing across cortical areas and layers, with no differences between cortical layers or among cortical areas. These phylogenetic differences may be related to shared life history variables and may reflect specific cognitive abilities.

Neuropeptide Y-immunoreactive neurons in the cerebral cortex of humans and other haplorrhine primates

We examined the distribution of neurons immunoreactive for neuropeptide Y (NPY) in the posterior part of the superior temporal cortex (Brodmann's area 22 or area Tpt) of humans and nonhuman haplorrhine primates. NPY has been implicated in learning and memory and the density of NPY-expressing cortical neurons and axons is reduced in depression, bipolar disorder, schizophrenia, and Alzheimer's disease. Due to the role that NPY plays in both cognition and neurodegenerative diseases, we tested the hypothesis that the density of cortical and interstitial neurons expressing NPY was increased in humans relative to other primate species. The study sample included great apes (chimpanzee and gorilla), Old World monkeys (pigtailed macaque, moor macaque, and baboon) and New World monkeys (squirrel monkey and capuchin). Stereologic methods were used to estimate the density of NPY-immunoreactive (-ir) neurons in layers I-VI of area Tpt and the subjacent white matter. Adjacent Nissl-stained sections were used to calculate local densities of all neurons. The ratio of NPY-ir neurons to total neurons within area Tpt and the total density of NPY-ir neurons within the white matter were compared among species. Overall, NPY-ir neurons represented only an average of 0.006% of the total neuron population. While there were significant differences among species, phylogenetic trends in NPY-ir neuron distributions were not observed and humans did not differ from other primates. However, variation among species warrants further investigation into the distribution of this neuromodulator system.

Neuropeptide Y and its role in CNS disease and repair

Neuropeptide Y (NPY) is widely expressed throughout the CNS and exerts a number of important physiological functions as well as playing a role in pathological conditions such as obesity, anxiety, epilepsy, chronic pain and neurodegenerative disorders. In this review, we highlight some of the recent advances in our understanding of NPY biology and how this may help explain not only its role in health and disease, but also its possible use therapeutically.

Compartment model of neuropeptide synaptic transport with impulse control

In this paper a mathematical description of a presynaptic episode of slow synaptic neuropeptide transport is proposed. Two interrelated mathematical models, one based on a system of reaction diffusion partial differential equations and another one, a compartment type, based on a system of ordinary differential equations (ODE) are formulated. Processes of inflow, calcium triggered activation, diffusion and release of neuropeptide from large dense core vesicles (LDCV) as well as inflow and diffusion of ionic calcium are represented. The models assume the space constraints on the motion of inactive LDCVs and free diffusion of activated ones and ions of calcium. Numerical simulations for the ODE model are presented as well. Additionally, an electronic circuit, reflecting the functional properties of the mathematically modelled presynaptic slow transport processes, is introduced.

Metabolism of amyloid-beta peptide and Alzheimer's disease

The accumulation of amyloid-beta peptide (Abeta), a physiological peptide, in the brain is a triggering event leading to the pathological cascade of Alzheimer's disease (AD) and appears to be caused by an increase in the anabolic activity, as seen in familial AD cases or by a decrease in catabolic activity. Neprilysin is a rate-limiting peptidase involved in the physiological degradation of Abeta in the brain. As demonstrated by reverse genetics studies, disruption of the neprilysin gene causes elevation of endogenous Abeta levels in mouse brain in a gene-dose-dependent manner. Thus, the reduction of neprilysin activity will contribute to Abeta accumulation and consequently to AD development. Evidence that neprilysin in the hippocampus and cerebral cortex is down-regulated with aging and from an early stage of AD development supports a close association of neprilysin with the etiology and pathogenesis of AD. Therefore, the up-regulation of neprilysin represents a promising strategy for therapy and prevention. Recently, somatostatin, which acts via a G-protein-coupled receptor (GPCR), has been identified as a modulator that increases brain neprilysin activity, resulting in a decrease of Abeta levels. Thus, it may be possible to pharmacologically control brain Abeta levels with somatostatin receptor agonists.

Alzheimer's disease, neuropeptides, neuropeptidase, and amyloid-beta peptide metabolism

Amyloid-beta peptide (Abeta), the pathogenic agent of Alzheimer's disease (AD), is a physiological metabolite in the brain. We have focused our attention and effort on elucidating the unresolved aspect of Abeta metabolism: proteolytic degradation. Among a number of Abeta-degrading enzyme candidates, we used a novel in vivo paradigm to identify a member of the neutral endopeptidase family, neprilysin, as the major Abeta catabolic enzyme. Neprilysin deficiency results in defects in the metabolism of endogenous Abeta 40 and 42 in a gene dose-dependent manner. Our observations suggest that even partial down-regulation of neprilysin activity, which could be caused by aging, can contribute to AD development by promoting Abeta accumulation. Moreover, we discuss the fact that an aging-dependent decline of neprilysin activity, which leads to elevation of Abeta concentrations in the brain, is a natural process that precedes AD pathology. In this Perspective, we hypothesize that neprilysin down-regulation has a role in sporadic AD (SAD) pathogenesis, and we propose that this knowledge be used for developing preventive and therapeutic strategies through use of a G protein-coupled receptor (GPCR).

Hippocampal plasticity in Alzheimer's disease

During recent years, many reports have indicated that in addition to the progressive neuropathology observed in Alzheimer's disease (AD), there are also plasticity-related changes in the AD brain. It is thought that these plastic events are an attempt by the brain either to try to restore structure and function or to compensate for the damage caused by the disease. Alternatively, it is possible that these changes are a part of the disease's pathologic cascade. Here we discuss our recent findings on highly polysialylated neural cell adhesion molecule (PSA-NCAM) and neuronal-expressed calcium-binding proteins in the hippocampus and entorhinal cortex of controls and patients with AD in relation to the other findings which suggest that structural plasticity is an integral part of the disease process of AD.

Neuropeptide Y, peptide YY and aluminum in Alzheimer's disease: is there an etiological relationship?

Neuropeptide Y (NPY) and peptide YY (PYY) are members of the pancreatic polypeptide family which have a high degree of primary and tertiary structural homology. They function as neurotransmitters and humoral agents in central nervous system and gastrointestinal function. During the last two decades, NPY body fluid concentrations and NPY/PYY brain receptor numbers have been demonstrated to be altered during the course of Alzheimer's disease. Recent research has shown that both NPY and PYY may be involved in aluminum metabolism in animal models. A brief discussion of the structure, biological activity and possible involvement of these peptides in aluminum metabolism and Alzheimer's disease is contained herein.

Phenylethanolamine N-methyltransferase (PNMT) gene and early-onset Alzheimer disease

The activity of human phenylethanolamine N-methyltransferase (PNMT) is reduced in the neurons of those cells in many subcortical areas of the brain that are known to undergo neurodegeneration in Alzheimer disease (AD). Others have reported that PNMT is decreased in brains of persons with AD and that the decrease in enzymatic activity is due to a reduced amount of the enzyme protein. We have previously described two polymorphisms, G-353A and G-148A, in the promoter region of the gene coding for PNMT. These markers were tested for their association with the occurrence of sporadic AD. Genotyping of 131 necropsy confirmed AD cases, and 947 adult nondemented controls were completed. We observed a significant association between both of the PNMT gene polymorphisms and early-onset AD (EOAD) (P < or = 0.007), but not in late-onset AD (LOAD). These data suggest that genetic variation in the promoter of the PNMT gene is associated with increased susceptibility to the sporadic form of EOAD.

Multiple receptors for neuropeptide Y in the hippocampus: putative roles in seizures and cognition

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions, including learning and memory. In addition, experimental studies have suggested that NPY, together with its receptors, may have a direct implication in several pathological disorders, including epilepsy/seizure. NPY-like immunoreactivity and NPY receptors have been shown to be present throughout the brain, but is concentrated in the hippocampus. The hippocampal formation has been repeatedly implicated in the modulation of cognition, as well as the pathogenesis of seizure. This review will concentrate on the hippocampal distribution of NPY, its receptors and the putative role played by this peptide in seizure, together with the regulation of cognitive function associated with learning and memory.

Selective lesion of the cholinergic basal forebrain causes a loss of cortical neuropeptide Y and somatostatin neurons

Degeneration of the cholinergic basal forebrain (CBF) and changes in cortical neuropeptide levels have been reported in Alzheimer's disease. In the present study, we sought to determine if a selective cholinergic lesion of nucleus basalis magnocellularis (Nbm) could affect the number and distribution of neuropeptide Y (NPY) and somatostatin (SS) immunoreactive neurons in the frontoparietal and occipital cortices of rats. Brain sections were evaluated at survival times of 1, 2, 4, 8, 12, 24, 48, 78 and 100 weeks after intraventricular injection of 192-saporin, an immunotoxin directed at the low affinity neurotrophin receptor (p75NGFr), that selectively destroys the CBF. Following the immunotoxin lesion of the Nbm, the number of NPY-labeled neurons decreased 33% in the frontoparietal cortex and 60% in the occipital cortex compared to age-matched normal controls at most survival time points. A significant loss of SS-labeled neurons in both cortical regions was seen 12 weeks after 192-saporin injection with no further change up to 100-week survival time. The effect of age on neuropeptidergic populations was evaluated in normal control rats. The number of NPY and SS immunoreactive neurons in aged rats (21-26 months) decreased by 42% in the frontoparietal cortex and 27% in the occipital cortex when compared with young (3-6 months) and middle-age (9-14 months) rats. When both non-lesioned and lesioned animals with different ages were pooled for linear regression, a significant correlation was found between the number of cortical NPY- and SS-labeled neurons and cortical acetylcholinesterase (AChE) histochemical staining intensity. These findings indicate that: (1) cholinergic denervation of the Nbm is associated with an irreversible loss of neocortical NPY and SS immunoreactive neurons analogous to that observed in Alzheimer's disease and aging; (2) the degree of the loss of cortical NPY and SS immunoreactive neurons seems to be related to the extent of the reduction of cortical AChE intensity in both toxin-injected and normal aged rats. These findings may reflect a trophic dependence of NPY and SS neurons on cortical cholinergic input.

Neuropeptide Y release from cultured hippocampal neurons: stimulation by glutamate acting at N-methyl-D-aspartate and AMPA receptors

L-Glutamate, N-methyl-D-aspartate, DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and kainate increased the release of neuropeptide Y-like immunoreactivity from primary cultures of rat hippocampal neurons incubated in Mg2+(1.2 mM)-containing medium. The neuropeptide Y-like immunoreactivity released by 100 microM glutamate was mainly accounted for by neuropeptide Y (1-36), but consisted in part (about 20%) of peptide YY. The effect of 100 microM glutamate on neuropeptide Y-like immunoreactivity release was largely (about 70%) prevented by the N-methyl-D-aspartate receptor antagonist dizocilpine maleate (10 microM), while the remainder (about 30%) was sensitive to the AMPA/ kainate receptor antagonist 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2-3-dione (10 microM). The AMPA(100 microM)-evoked release of neuropeptide Y-like immunoreactivity was strongly antagonized by 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2-3-dione and by 1-aminophenyl-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine, but it was in part (15-20%) sensitive to dizocilpine. The releases of neuropeptide Y-like immunoreactivity elicited by glutamate, N-methyl-D-aspartate, AMPA and kainate were all strongly Ca(2+)-dependent. Tetrodotoxin (1 microM) abrogated the N-methyl-D-aspartate-evoked release and partly inhibited the release caused by glutamate, but did not modify significantly AMPA- or kainate-evoked release. Removal of Mg2+ from the medium caused increase of neuropeptide Y-like immunoreactivity release, an effect prevented by dizocilpine maleate or 7-Cl-kynurenate. Cyclothiazide (10 microM), a drug known to prevent AMPA receptor desensitization, enhanced the neuropeptide Y-like immunoreactivity release elicited by 100 microM AMPA, but not that caused by 100 microM kainate. However, when used at a lower concentration (50 microM), kainate elicited a response that was potentiated significantly by cyclothiazide. It is concluded that glutamate can stimulate Ca(2+)-dependent release of neuropeptide Y from hippocampal neurons mainly through N-methyl-D-aspartate receptors and, less so, by activating cyclothiazide-sensitive receptors of the AMPA-preferring type.

Localization of neuropeptide Y Y1 mRNA in the human brain: abundant expression in cerebral cortex and striatum

Many neurobiological functions have been ascribed to the NPY Y1 receptor subtype, but autoradiographic analysis has failed to detect Y1 binding sites in most human brain areas, in contrast to the rat. We examined the regional distribution of Y1 mRNA-containing cells in the post-mortem human brain to clarify if there is a major species difference in terms of the existence of Y1 receptors in the human telencephalon, in particular the striatum and cortex. In situ hybridization experiments revealed widespread distribution of Y1 mRNA signals in all layers of most limbic and neocortical regions, predominantly in layer IV (most cortical regions) and layer VI. The striatum showed moderate Y1 receptor mRNA expression levels with intensely expressing cells localized to the nucleus accumbens. The highest Y1 receptor mRNA expression was apparent within the dentate gyrus, and the lowest in the subiculum, parahippocampal gyrus, cerebellum, and thalamus. In vitro autoradiography using [125I]Leu31Pro34-PYY and [125I]PYY with NPY (13-36) or Leu31Pro34-NPY, confirmed the presence of low Y1-like binding in the human brain despite abundant Y1 mRNA expression. However, using a rat model of the human autopsy process, it was apparent that the inability to reveal high Y1- versus Y2-like receptors in the human brain was related in part to marked reductions of Y1-like, but not Y2-like, receptors within a 4 h post-mortem delay. Altogether, the results indicate that the Y1 receptor gene is abundant in the human brain and this receptor may have important roles in cognitive, limbic and motor function.

Age-related changes of VIP, NPY and somatostatin-immunoreactive neurons in the cerebral cortex of aged rats

Recent studies have explored certain changes with aging of neurons containing neuropeptides. The degree of loss of vasoactive intestinal polypeptide (VIP)-, neuropeptide Y (NPY)- and somatostatin-containing neurons in the aged CNS has not yet been established with certainty however, and available data is often contradictory. Changes with aging of VIP- and NPY-containing neurons were demonstrated by immunocytochemistry in this study. A major loss of VIP-immunoreactive (ir) neurons in aged rat brain was observed in the frontal cortex area 3, parietal cortex area 1, hindlimb area, temporal cortex area 1 and 2, monocular part of occipital cortex area 1, occipital cortex area 2, and retrosplenial cortex. VIP-ir cells in the frontal cortex areas 1 and 2, parietal cortex area 2, forelimb area, binocular part of the occipital cortex area 1, and the dentate gyrus were moderately decreased. The axis of VIP neurons in the aged group showed an irregular orientation tendency, especially in layers II and III. Major loss of NPY-ir neurons in aged rat brain were observed in the retrosplenial cortex, frontal cortex areas 1 and 2, parietal cortex areas 1 and 2, occipital cortex areas 1 and 2, the temporal cortex, hippocampus proper and cingulate cortex. Loss of NPY-ir neurons was observed mostly in layers V and VI. The number and length of dendritic branches also appeared to have decreased and shortened in the aged group. There were only slight decreases of somatostatin-ir cell numbers in the parietal and occipital cortex of the aged group. These results indicate the involvement of VIP and NPY-ir neurons in the aging process of cerebral cortex, and provide the morphological evidence for the decreased number of VIP and NPY neurons by immunocytochemistry in each area of cerebral cortex of aged rats.

Neuronal nitric oxide synthase (nNOS) mRNA expression and NADPH-diaphorase staining in the frontal cortex, visual cortex and hippocampus of control and Alzheimer's disease brains

Neuronal nitric oxide synthase (nNOS) mRNA levels and NADPH diaphorase (NADPH-d) staining were compared in the frontal cortex, visual cortex and hippocampus (dentate gyrus and CA subfields of Ammon's horn) of five Alzheimer's disease (AD) and six control brains. The cellular abundance of nNOS mRNA was quantified by in-situ hybridisation using 35S-labelled antisense oligonucleotides complementary to the human nNOS sequence. Although the mean level of nNOS expression was decreased in all three regions in AD cases as compared to controls, it did not reach significance. Neurones positively labelled for nNOS mRNA and neurones positive for NADPH-d histochemistry displayed similar distribution in control and AD cases. In AD brains the density of neurones having detectable levels of nNOS mRNA was significantly decreased in the white matter underlying the frontal cortex (P < 0.05) but not in the frontal cortex gray matter; no change was observed in the gray or white matter of the visual cortex in AD. The number of cells expressing detectable levels of nNOS mRNA in the hippocampus was also significantly decreased (P < 0.05) in AD. The density of NADPH-d-positive cells was not significantly decreased in the gray or white matter of the frontal or visual cortices in AD compared to controls; however, the number of NADPH-d-positive cells was significantly decreased in the hippocampus (P < 0.01). These data indicate that although the cellular abundance of nNOS mRNA is not significantly decreased in these three regions in AD, there is a significant decrease in the number of cells expressing detectable levels of nNOS mRNA in the white matter underlying the frontal cortex and in the dentate gyrus and CA subfields of the hippocampus in AD. Furthermore, there was also a significant decrease in the number of NADPH-d-positive cells in the dentate gyrus and CA subfields of the hippocampus in AD as compared to controls. These results suggest specific populations of nNOS/NADPH-d cells in the white matter underlying the frontal cortex and in the hippocampus are vulnerable in AD. The implications of these findings are discussed.

Age-related change of neuropeptide Y-immunoreactive neurons in the cerebral cortex of aged rats

Recent studies have explored certain changes with aging of neurons containing neuropeptides. The extent of loss in aged central nervous system (CNS) of neuronal cells containing neuropeptide Y (NPY) has not yet been established with certainty, and available data is often contradictory. Changes of NPY-containing neurons with aging in the cerebral cortex of aged rat were demonstrated by immunocytochemistry. A major loss of NPY-immunoreactive (ir) neurons in the aged rat brain was observed in the retrosplenial cortex, frontal cortex area 1 and 2, parietal cortex area 1 and 2, occipital cortex area 1 and 2, temporal cortex area 3, cingulate cortex and the hippocampus proper. A loss of NPY-ir neurons was observed mostly in layers V and VI; in addition, the number and length of dendritic branches appeared to be decreased and shortened in the age group. These results indicate the involvement of NPY-ir neurons in the aging process of cerebral cortex, and provide the first morphological evidence for the loss of NPY neurons in the cerebral cortex of aged rats.

Patterns of synaptic and nerve cell pathology in Alzheimer's disease

Recent neuropathological evidence suggests that synapse pathology is the major correlate of cognitive decline in Alzheimer's disease (AD) patients, but also in other dementia syndromes. We suggest that synapse loss in AD-patients mainly reflects neuronal destruction in other iso- and allocortical areas as well as in brain stem nuclei. In addition an impaired compensatory synaptogenesis may contribute to the reduction in synaptic connectivity. The patterns of cell death in AD-brains determined by analysis of DNA-fragmentation in situ revealed significantly higher numbers of dying cells (neurons as well as glia cells) in AD-brains compared to controls. Amyloid deposition as well as neurofibrillary pathology apparently do not induce cell death directly, but may increase the risk of cells to die in response to additional minor metabolic insults. We propose that multiple pathogenetic factors are involved in the reduction of synaptic connectivity in AD-brains, which finally is reflected in the decline of cognitive functions.

Neuropeptide deficits in schizophrenia vs. Alzheimer's disease cerebral cortex

Neuropeptide concentrations were determined in the postmortem cerebral cortex from 19 cognitive-impaired schizophrenics, 4 normal elderly subjects, 4 multi-infarct dementia (MID) cases, and 13 Alzheimer's disease (AD) patients. Only AD patients met criteria for AD. The normal elderly and MID cases were combined into one control group. Somatostatin concentrations were reduced in both schizophrenia and AD. Neuropeptide Y concentrations were reduced only in schizophrenia, and corticotropin-releasing hormone concentrations were primarily reduced in AD. Concentrations of vasoactive intestinal polypeptide and cholecystokinin also were reduced in schizophrenia, although not as profoundly as somatostatin or neuropeptide Y. In AD, cholecystokinin and vasoactive intestinal peptide were unchanged. Neuropeptide deficits in schizophrenics were more pronounced in the temporal and frontal lobes than in the occipital lobe. The mechanisms underlying these deficits in schizophrenia and AD are likely distinct. In schizophrenia, a common neural element, perhaps the cerebral cortical gaba-aminobutyric acid (GABA)-containing neuron, may underlie these deficits.

The neurochemistry of Alzheimer type, vascular type and mixed type dementias compared

We present the results of a meta-analysis of neurochemical changes in human post mortem brains of Alzheimer type (AD), vascular type (VD) and mixed type (MF) dementias, and matched controls based on 275 articles published between January 1980 and February 1994. Severity of degeneration between the different neurochemical systems is as follows, although ranking is difficult with regard to limited numbers of investigations in some neurochemical systems: Cholinergic system > serotonergic system > excitatory amino acids > GABAergic system > energy metabolism > NA > oxidative stress parameters > neuropeptides > DA. But, within a neurochemical system, degeneration is not evenly distributed. Spared parameters, e.g. muscarinic receptors and MAO-B, allow to make some suggestions for future therapeutic strategies.

Neuropeptide changes in cortical and deep gray structures in Alzheimer's disease

The alteration of certain neuropeptide levels is a dramatic and consistent finding in the brains of AD patients. Levels of SS, which is normally present in high concentrations in cerebral cortex /75/, are consistently decreased in the neocortex, hippocampus and CSF of AD patients. In addition, decreased levels of SS correlate regionally with the distribution of neurofibrillary tangles in AD /47/. Most available evidence suggests that the subset of SS-containing neurons which lack NADPH diaphorase may be relatively vulnerable to degeneration in AD. CRF is another neuropeptide with frequently observed changes in AD. Levels of CRF, which is normally present in low concentrations in cortical structures /75/, are decreased in the neocortex and hippocampus of AD patients. However, levels of CRF in the CSF of AD patients are not consistently reduced, but this is likely a reflection of the relatively low levels of CRF normally present in cerebral cortex. Studies of deep gray structures in AD brains reveal elevated levels of GAL in the nucleus basalis. The ability of GAL to inhibit cholinergic neurotransmission has generated considerable interest, since degeneration of cholinergic neurons in the basal forebrain consistently occurs in AD. In addition, the presence of NADPH diaphorase in GAL-containing neurons may underlie the relative resistance of these neurons to degeneration. From the aforementioned studies, it appears that the neurons which are relatively resistant to neurodegeneration in AD contain NADPH diaphorase. It is hypothesized that the presence of NADPH diaphorase protects these neurons from neurotoxicity mediated by glutamate or nitric oxide. Although one recent study /147/ has reported an elevation of the microtubule-associated protein tau in the CSF of AD patients (and this could become a useful antemortem diagnostic tool for AD), no similar CSF abnormality has been found for any of the neuropeptides. Thus, the measurement of CSF neuropeptide levels presently remains unhelpful in the diagnosis and treatment of AD. Future research on neuropeptides and their potential roles in the pathogenesis, diagnosis, and treatment of AD will likely involve further development of pharmacological modulators of neuropeptide systems, together with the further study of brain neuropeptidases.

Plasma neuropeptide Y is reduced in patients with Alzheimer's disease

Neuropeptide Y (NPY) is demonstrated to be involved in the pathophysiology of Alzheimer's disease, as well as somatostatin. We measured the plasma NPY content in patients with Alzheimer's disease and healthy control subjects (n = 25) by HPLC coupled with radioimmunoassay. The difference in screening pattern of NPY-like immunoreactivity in 50 fractions eluted by HPLC obtained from the plasma peptide-rich fraction between patients with Alzheimer's disease and healthy controls suggested the abnormal metabolism of plasma NPY in patients with Alzheimer's disease. Plasma NPY in patients with Alzheimer's disease was significantly decreased compared with that in healthy controls, which was compatible with the findings obtained from the brain and cerebrospinal fluid and could be involved in the pathogenesis or pathophysiology of Alzheimer's disease.

Tau protein concentrations in cerebrospinal fluid of patients with dementia of the Alzheimer type

Tau protein concentrations were measured in the CSF of 23 patients with dementia of the Alzheimer type (DAT), 36 patients with multi-infarct dementia (MID), and 23 control subjects. Tau protein concentrations were significantly higher in patients with DAT than in controls (P < 0.001) and patients with MID (P < 0.001). A significantly positive correlation between CSF tau protein and glucose concentrations (r = 0.79, P < 0.001) and evolution of disease (r = 0.47, P < 0.05), and a negative correlation with Folstein's mental state examination test (r = -0.73, P < 0.001) were found in patients with DAT.

Decrease in cerebellin and corticotropin-releasing hormone in the cerebellum of olivopontocerebellar atrophy and Shy-Drager syndrome

Four neuropeptides; cerebellin, corticotropin-releasing hormone (CRH), neuropeptide Y and somatostatin were studied by radioimmunoassay in the postmortem human brains obtained from three patients with olivopontocerebellar atrophy (OPCA) and one with Shy-Drager syndrome. Significant decreases in cerebellin and CRH concentrations were found in the cerebellar hemisphere of these diseases compared with controls. These findings suggest important pathophysiological roles of cerebellin and CRH in these cerebellar diseases. Such significant decreases were not found in neuropeptide Y and somatostatin.

Central nervous system pharmacology of neuropeptide Y

Neuropeptide Y (NPY) is a 36-amino acid peptide belonging to the pancreatic polypeptide family that has marked and diverse biological activity across species. NPY originally was isolated from mammalian brain tissue somewhat more than 10 years ago and, since that time, has been the subject of numerous scientific publications. NPY and its proposed three receptors (Y1, Y2 and Y3) are relatively abundant in and uniquely distributed throughout the brain and spinal cord. This review will highlight the results from a number of research-oriented studies that have examined how NPY is involved in CNS function and behavior, and how these studies may relate to the possible development of medicines, either NPY-like agonists or antagonists, directed towards the treatment of disorders such as anxiety, pain, hypertension, schizophrenia, memory dysfunction, abnormal eating behavior and depression.

Neuropeptide Y immunoreactive neurons in murine trisomy 16 cortical cultures. Plasticity of expression and differentiation

Neuropeptide Y (NPY)-containing neurons are depleted in the cortices of individuals with Alzheimer disease (AD), yet spared in the striatum of patients with Huntington chorea. It is unknown whether this neuronal phenotype is inherently susceptible to the neurodegenerative processes that are a hallmark of AD. To study this question, the murine trisomy 16 model of Down syndrome and Alzheimer disease was investigated. Since trisomic fetuses die in utero, studies were carried out on primary cultures of dissociated cortical neurons. These were prepared from 15-d gestational trisomy 16 fetuses and their littermate euploid controls, and examined by immunocytochemical staining for neuropeptide Y at 7 and 12 d in vitro. Trisomy 16 neurons were also grown on euploid glial carpets, whereas euploid neurons were grown on trisomic glia. The results demonstrate a significant increase in the number of NPY neurons and a stunting in the dendritic arbor of these neurons in trisomic vs euploid cortex. Both of these parameters could be normalized by direct contact with euploid glia. When euploid cortex was plated on trisomic glia, the number of NPY neurons and their morphology were altered so that they began to resemble trisomic NPY cortical neurons. These results indicate a dysregulation of NPY neuronal expression and differentiation in trisomy 16 cortex that are modifiable by interaction with euploid glia and imply an abnormal trophic (glial) environment in trisomic cortex.

Cortical and subcortical neuropeptides in Alzheimer's disease

Given the clinical features of AD, the severe atrophy of cerebral cortex that accompanies the disease, and the predominant cortical location of plaques and tangles, it is not surprising to find the most consistent changes in neuropeptides in this disease occurring in the cerebral cortex. The neuropeptide changes that have been reproducibly demonstrated in AD are reduced hippocampal and neocortical SS and CRF concentrations and a reduced CSF level of SS. In cerebral cortex, SS and CRF are found in GABAergic local circuit neurons in layers II, III, and VI. The function of these neurons is not well established, although these cells may act to integrate the flow of incoming and outgoing information in cerebral cortex. If this is true, then dysfunction of this integration could produce widespread failure of cerebrocortical function, resulting in the various neurobehavioral deficits seen in AD. The interpretation of neuropeptide changes in subcortical brain regions, either those that project to cortex, or those that are the efferent targets of cortical projections, is also uncertain. The observed neuropeptide abnormalities in these brain regions in AD are less consistent than are those seen in cerebral cortex. Perhaps the most intriguing result in these regions is the increases in galanin-immunoreactive terminals seen in the nucleus basalis of AD brains. Galanin has been shown to inhibit acetylcholine release and to impair memory function in rats (46,113).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of interleukin-1 beta and beta 2-microglobulin with neuropeptides in cerebrospinal fluid of patients with dementia of the Alzheimer type

We studied interleukin-1 beta (IL-1 beta), beta 2-microglobulin (beta 2-m), beta-endorphin, substance P, neuropeptide Y and somatostatin concentrations in the cerebrospinal fluid of 13 patients with dementia of the Alzheimer type (DAT), 13 patients with multi-infarct dementia (MID) and 15 age-matched control subjects. Substance P was significantly lower in DAT than in controls (P < 0.05), as well as somatostatin in DAT as compared to both controls (P < 0.01) and MID (P < 0.05), whereas beta 2-m was higher in DAT than in controls (P < 0.01). Neuropeptide Y, beta-endorphin and IL-1 beta showed similar concentrations in the three groups studied. A significantly positive correlation was observed between IL-1 beta and substance P (r = 0.79, P < 0.01) and somatostatin (r = 0.75, P < 0.05) in DAT, which was not observed in MID. In addition, beta 2-m showed a negative correlation with IL-1 beta (r = -0.73, P < 0.05) in DAT, and age correlated negatively with IL-1 beta in controls and MID, but positively in DAT. Therefore, these results support the idea that an altered relationship may exist in Alzheimer's disease between the nervous and immune system.

Reduced cerebral cortical but elevated striatal concentration of somatostatin-like immunoreactivity in dominantly inherited olivopontocerebellar atrophy

Somatostatin-like immunoreactivity (SLI) was measured in the brains of nine patients with dominantly inherited olivopontocerebellar atrophy (OPCA), who all had a marked deficit of the cholinergic marker choline-acetyltransferase (ChAT) in the cerebral cortex and striatum. Mean concentrations of SLI in OPCA were significantly reduced by 42-58% in parietal and occipital cortices and frontal cortical eye fields, but were normal in other cortical areas, including two subdivisions of the temporal cortex which show marked depletions of both SLI and ChAT in Alzheimer's disease. This dissociation of SLI and ChAT indicates that a cortical cholinergic deficit does not invariably lead to reduction of somatostatin. In the caudate nucleus, the region of OPCA brain having the most severe ChAT deficit (-81%), SLI levels were significantly elevated by 46% and were negatively and significantly correlated with ChAT activities (r = -0.66). The SLI alterations could be due to abnormal somatostatin metabolism or release, or an increased number of somatostatin-containing neurons and could contribute to the brain dysfunction of OPCA.

Cultured GABA-immunoreactive neurons are resistant to toxicity induced by beta-amyloid

Neurodegeneration in Alzheimer's disease is characterized by a selective loss of particular cell populations. Several recent lines of evidence suggest that beta-amyloid protein directly contributes to the disease's progression and is likely responsible for the observed pattern of neuronal death. We have previously demonstrated that aggregated beta-amyloid peptides are neurotoxic to cultured neurons. We now report that a neuronal population exhibiting GABA-immunoreactivity is resistant to beta-amyloid-induced toxicity in vitro, a finding consistent with observations in the Alzheimer brain. Determination of the intrinsic neuronal characteristics responsible for resistance to beta-amyloid may prove beneficial in both understanding the mechanism(s) of beta-amyloid neurotoxicity and halting the disease's progressive neuronal degeneration.

Modulation of neuropeptide Y expression in rat brain neuronal cultures

Neuropeptide Y (NPY) and its encoding mRNA were measured in neurons co-cultured from rat basal forebrain and cerebral cortex. NPY was synthesized and released in a manner consistent with secretion-synthesis coupling; depolarization increased each in a calcium-dependent manner. The accumulation of NPY encoding mRNA was elevated by a muscarinic receptor blocker, without changes in transmitter release or peptide synthesis, thereby consistent with a membrane potential-independent mechanism. Changes in intrinsic muscarinic transmission could nonetheless be expressed rapidly as an elevation in NPY levels by depolarizing the neurons subsequent to muscarinic receptor blockade. This depolarization-induced elevation of NPY subsequent to muscarinic receptor blockade was dependent on the presence of extracellular calcium ions. Forskolin and pertussis toxin also increased NPY encoding mRNA levels in a manner that was not additive with muscarinic receptor blockade. These results suggest that one or more muscarinic receptors may tonically modulate NPY synthesis via changes in adenylate cyclase activity, providing a model for the non-homeostatic modulation of neuropeptide turnover.