Reduced lumbar CSF somatostatin levels in Alzheimer's disease

Molecular Mechanisms and Aspects on the Role of Neuropeptide Y as a Zn2+ and Cu2+ Chelator

The concept of metal chelation is based on simple coordination chemistry. The development of an ideal metal chelator that completely and selectively removes toxic metals from a specific metal binding site in proteins is required to prevent and or inhibit a variety of diseases, among them neurodegenerative diseases. This work examines neuropeptide Y (NPY) as a Zn²⁺ and Cu²⁺ chelator agent. NPY is a natural peptide that is produced in the human body; therefore, it is not a toxic agent and the complex that it forms is not toxic as well. Our simulations reveal that NPY has an efficient Zn²⁺ chelation activity but is less effective in chelating Cu²⁺. Moreover, while NPY demonstrates several conformations, the metal chelation occurs more efficiently in its native structure. Beyond the exploration of the activity of NPY as a Zn²⁺ and Cu²⁺ chelator agent, this work provides an insight into the molecular mechanisms of the chelation of these metals at the molecular level. The outcomes from this work may guide future experimental studies to examine NPY in metal chelation therapy for neurodegenerative diseases.

Interneurons, tau and amyloid-β in the piriform cortex in Alzheimer's disease

Impaired olfaction has been described as an early symptom of Alzheimer's disease. Neuroanatomical changes underlying this deficit in the olfactory system are largely unknown. Interestingly, neuropathology begins in the transentorhinal cortex and extends to the neighboring limbic system and basal telencephalic structures that mediate olfactory processing, including the anterior olfactory nucleus and olfactory bulb. The human piriform cortex has been described as a crucial area in odor quality coding; disruption of this region mediates early olfactory deficits in Alzheimer's disease. Most neuropathological investigations have focused on the entorhinal cortex and hippocampus, whereas the piriform cortex has largely been neglected. This work aims to characterize the expression of the neuropathological amyloid-β peptide, tau protein and interneuron population markers (calretinin, parvalbumin and somatostatin) in the piriform cortex of ten Alzheimer-diagnosed (80.4 ± 8.3 years old) and five control (69.6 ± 11.1) cases. Here, we examined the distribution of different interneuronal markers as well as co-localization of interneurons and pathological markers. Results indicated preferential vulnerability of somatostatin- (p = 0.0001 < α = 0.05) and calretinin-positive (p = 0.013 < α = 0.05) cells that colocalized with amyloid-β peptide, while the prevalence of parvalbumin-positive cells was increased (p = 0.045 < α = 0.05) in the Alzheimer's cases. These data may help to reveal the neural basis of olfactory deficits linked to Alzheimer's disease as well as to characterize neuronal populations preferentially vulnerable to neuropathology in regions critically involved in early stages of the disease.

Transmitter deficits in Alzheimer's disease

The pattern of neurotransmitter pathway losses in Alzheimer's disease are reviewed. Deficits of the cholinergic pathway from the nucleus basalis, the noradrenergic pathway from the locus coeruleus and the serotoninergic pathway from the raphe nuclei are established. Cortical somatostatin interneurons are affected and dopaminergic neurons may be affected although these may be late or secondary phenomena in the disease process. Other neuronal systems, particularly in the hippocampus and temporal cortex, are also damaged. However, the disease is not one of generalised neuronal atrophy since some neurons are selectively spared. The established pathway-specific losses are discussed in relation to the clinical symptomatology and the pathology of the disorder. The biochemical and histological findings are compared with similar measurements made on tissues from other dementing disorders in an attempt to trace features common to dementias. Finally, as an addendum, a hypothesis is briefly outlined which attempts to explain the common features of the affected neurons and the pathogenesis of the disorder.

Distinct modulation of microglial amyloid β phagocytosis and migration by neuropeptides (i)

Microglial activation plays an integral role in the development and course of neurodegeneration. Although neuropeptides such as bradykinin (BK), somatostatin (SST), and endothelin (ET) are known to be important mediators of inflammation in the periphery, evidence of a similar function in brain is scarce. Using immunocytochemistry, we demonstrate the expression of receptors for BK (B1, B2 subtypes), ET (ETA, ETB subtypes) and SST (SST 2, 3, 4 subtypes) in primary microglia and microglial cell lines. Exposure of BV2 and N9, as well as primary microglial cells to BK or SST increased Aβ uptake in a concentration-dependent manner, whereas endothelin decreased Aβ uptake. This was caused by increased phagocytosis of Aβ since the rate of intracellular Aβ degradation remained unaffected. All neuropeptides increased chemotactic activity of microglia. In addition, BK reduced Aβ-induced expression of proinflammatory genes including iNOS and COX-2. ET decreased the Aβ-induced expression of monocyte chemoattractant protein 1 and interleukin-6. These results suggest that neuropeptides play an important role in chemotaxis and Aβ clearance and modulate the brain's response to neuroinflammatory processes.

Concerted changes in transcripts in the prefrontal cortex precede neuropathology in Alzheimer's disease

Using the Braak staging for neurofibrillary changes as an objective indicator of the progression of Alzheimer's disease, we have performed a systematic search for global gene expression changes in the prefrontal cortex during the course of Alzheimer's disease. In the prefrontal cortex, senile plaques and neurofibrillary changes start to appear around Braak stage III, allowing for the detection of changes in gene expression before, during and after the onset of Alzheimer's disease neuropathology. Two distinct patterns of tightly co-regulated groups of genes were observed: (i) an increase in expression in early Braak stages, followed by a decline in expression in later stages (the UPDOWN clusters; containing 865 genes) and (ii) a decrease in expression in early Braak stages, followed by an increase in expression in later stages (the DOWNUP clusters; containing 983 genes). The most profound changes in gene expression were detected between Braak stages II and III, just before or at the onset of plaque pathology and neurofibrillary changes in the prefrontal cortex. We also observed an increase in intracellular beta amyloid staining from Braak stages I to III and a clear decrease in Braak stages IV to VI. These data suggest a link between specific gene expression clusters and Alzheimer's disease-associated neuropathology in the prefrontal cortex. Gene ontology over-representation and functional gene network analyses indicate an increase in synaptic activity and changes in plasticity during the very early pre-symptomatic stage of the disease. In later Braak stages, the decreased expression of these genes suggests a reduction in synaptic activity that coincides with the appearance of plaque pathology and neurofibrillary changes and the clinical diagnosis of mild cognitive impairment. The interaction of the ApoE genotype with the expression levels of the genes in the UPDOWN and DOWNUP clusters demonstrates that the accelerating role of ApoE-ε4 in the progression of Alzheimer's disease is reflected in the temporal changes in gene expression presented here. Since the UPDOWN cluster contains several genes involved in amyloid precursor protein processing and beta amyloid clearance that increase in expression in parallel with increased intracellular beta amyloid load, just before the onset of plaque pathology in the prefrontal cortex, we hypothesize that the temporally orchestrated increase in genes involved in synaptic activity represents a coping mechanism against increased soluble beta amyloid levels. As these gene expression changes occur before the appearance of Alzheimer's disease-associated neuropathology, they provide an excellent starting point for the identification of new targets for the development of therapeutic strategies aimed at the prevention of Alzheimer's disease.

Predator stress induces behavioral inhibition and amygdala somatostatin receptor 2 gene expression

Psychological stressors precipitate and maintain stress-induced psychopathology, and it is likely that altered amygdala function underlies some of the deleterious effects of psychological stress. To understand the mechanisms underlying the linkage between the response to psychological stressors and maladaptive or psychopathological responses, we have focused on amygdala responsivity in animal models employing species-specific psychological stressors. In the present study, we characterized the effects of a 15-min exposure to a natural predator, the ferret, on rat behavior and the expression of the somatostatin family of genes in the amygdala. We examined the somatostatin family of genes because substantial evidence shows that central somatostatin systems are altered in various neuropsychiatric illnesses. We report that rats respond to acute ferret exposure with a significant increase in fearful and anxious behaviors that is accompanied by robust amygdala activation and an increase in somatostatin receptor 2 (sst2) messenger RNA expression within the amygdala and anterior cingulate cortex. These studies are the first to show stress-induced changes in amygdala sst2 expression and may represent one mechanism by which psychological stress is linked to adaptive and maladaptive behavioral responses.

Chronic but not acute intracerebroventricular administration of amyloid beta-peptide(25-35) decreases somatostatin content, adenylate cyclase activity, somatostatin-induced inhibition of adenylate cyclase activity, and adenylate cyclase I levels in the rat hippocampus

Although alterations in adenylate cyclase (AC) activity and somatostatin (SRIF) receptor density have been reported in Alzheimer's disease, the effects of amyloid beta-peptide (Abeta) on these parameters in the hippocampus are unknown. Our aim was to investigate whether the peptide fragment Abeta(25-35) can affect the somatostatinergic system in the rat hippocampus. Hence, Abeta(25-35) was injected intracerebroventricularly (i.c.v.) to Wistar rats in a single dose or infused via an osmotic minipump connected to a cannula implanted in the right lateral ventricle during 14 days. The animals were decapitated 7 or 14 days after the single injection and 14 days after chronic infusion of the peptide. Chronic i.c.v. infusion of Abeta(25-35) decreased SRIF-like immunoreactive content without modifying the SRIF receptor density, SRIF receptor expression, or the Gialpha(1), Gialpha(2), and Gialpha(3) protein levels in the hippocampus. This treatment, however, caused a decrease in basal and forskolin-stimulated AC activity as well as in the capacity of SRIF to inhibit AC activity. Furthermore, the protein levels of the neural-specific AC type I were significantly decreased in the hippocampus of the treated rats, whereas an increase in the levels of AC V/VI was found, with no alterations in type VIII AC. A single i.c.v. dose of Abeta(25-35) exerted no effect on SRIF content or SRIF receptors but induced a slight decrease in forskolin-stimulated AC activity and its inhibition by SRIF. Because chronic Abeta(25-35) infusion impairs learning and memory whereas SRIF facilitates these functions, the alterations described here might be physiologically important given the decreased cognitive behavior previously reported in Abeta-treated rats.

β-Amyloid increases somatostatin expression in cultured cortical neurons

In beta-amyloid (Abeta)-induced neurotoxicity, activation of the NMDA receptor, increased Ca2+ and oxidative stress are intimately associated with neuronal cell death as normally seen in NMDA-induced neurotoxicity. We have recently shown selective sparing of somatostatin (SST)-positive neurons and increased SST expression in NMDA agonist-induced neurotoxicity. Accordingly, the present study was undertaken to determine the effect of Abeta25-35-induced neurotoxicity on the expression of SST in cultured cortical neurons. Cultured cortical cells were exposed to Abeta25-35 and processed to determine the cellular content and release of SST into medium by radioimmunoassay and SST mRNA by RT-PCR. Abeta25-35 induces neuronal cell death in a concentration- and time-dependent fashion, increases SST mRNA synthesis and induces an augmentation in the cellular content of SST. No significant changes were seen on SST release at any concentration of Abeta25-35 after 24 h of treatment. However, Abeta25-35 induces a significant increase of SST release into medium only after 12 h in comparison with other time points. Most significantly, SST-positive neurons are selectively spared in the presence of a lower concentration of Abeta25-35, whereas, in the presence of higher concentrations of Abeta25-35 for extended time periods, SST-positive neurons decrease gradually. Furthermore, Abeta25-35 induces apoptosis at lower concentrations (5 and 10 micromol/L) and necrosis at higher concentrations (20 and 40 micromol/L). Consistent with the increased accumulation of SST, these data suggest that Abeta25-35 impairs cell membrane permeability. Selective sparing of SST-positive neurons at lower concentrations of Abeta25-35 at early time points directly correlates with the pathophysiology of Alzheimer's disease.

Processing of neuropeptide Y, galanin, and somatostatin in the cerebrospinal fluid of patients with Alzheimer's disease and frontotemporal dementia

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are two prevalent neurodegenerative disorders for which the causes are unknown, except in rare familial cases. Several changes in neuropeptide levels as measured by radioimmunoassay (RIA) have been observed in these illnesses. Somatostatin (SOM) levels in cerebrospinal fluid (CSF) are consistently decreased in AD and FTD. Neuropeptide Y (NPY) levels are decreased in AD, but normal in FTD. Galanin (GAL) levels increase with the duration of illness in AD patients. The majority of studies of neuropeptides in CSF have not been verified by HPLC. The observed decrease in a neuropeptide level as measured by RIA may therefore reflect an altered synthesis or extracellular processing, resulting in neuropeptide fragments that may or may not be detected by RIA. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-MS) has been shown to be a powerful technique in the analysis of biological materials without any pre-treatment, by detecting peptides and proteins at a specific mass-to-charge (m/z) ratio. We studied the processing of the neuropeptides NPY, NPY, SOM and GAL in the cerebrospinal fluid of patients with AD (n = 3), FTD (n = 3) and controls (n = 2) using MALDI-MS. We found that considerable inter-individual variability exists in the rate of neuropeptide metabolism in CSF, as well as the number of peptide fragments formed. Certain patients showed differences in the processing of specific neuropeptides, relative to other patients and controls. This analysis of the metabolic processing of neuropeptides in CSF yielded a large amount of data for each individual studied. Further studies are required to determine the changes in neuropeptide processing that can be associated with AD and FTD. With further investigations using MALDI-MS analysis, it may be possible to identify a neuropeptide fragment or processing enzyme that can be correlated to these disease states.

Processing of neuropeptide Y and somatostatin in human cerebrospinal fluid as monitored by radioimmunoassay and mass spectrometry

The processing of four neuropeptides, neuropeptide Y (NPY) 1-36, NPY (18-36), somatostatin (SOM) 1-28, and SOM (15-28) was studied in human cerebrospinal fluid (CSF) by using a novel combination of methods that included radioimmunoassay (RIA) and mass spectrometry. Untreated CSF samples were chromatographed using reversed-phase high pressure liquid chromatography (RP-HPLC) followed by NPY-RIA or SOM-RIA. These results were compared with those obtained by incubating CSF with exogenous synthetic peptides and directly detecting peptide fragments by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). Using this combination of methods, we were able to determine the probable identities of peptides/peptide fragments recognized in radioimmunoassays. The most important NPY-immunoreactive components in CSF were found to be NPY (1-36) and NPY (3-36). Metabolic products of SOM (15-28) were found to contribute to SOM-like immunoreactivity (SOM-LI) in CSF, but SOM (1-28) only to a lesser degree. Differences in the rate of neuropeptide processing were observed. These differences depended more on the length of the peptide than its sequence. NPY (18-36) and SOM (15-28) were rapidly and extensively processed, whereas NPV (1-36) and SOM (1-28) were processed much more slowly in CSF. The production of SOM (15-28) from SOM (1-28) by enzymes in CSF was not observed. Also, the presence of a disulfide bond in the somatostatins appeared to stabilize them against enzymatic digestion of the ring structure. The results detailed in this report confirm MALDI-MS important role in studies of neuropeptide processing in CSF.

The significance of the activity of CSF cholinesterases in dementias

This article reviews the significance of changes in the level of cerebrospinal fluid acetylcholinesterase or cholinesterase in patients with Alzheimer's disease or other dementias. Evidence has shown that the methodology of assaying cerebrospinal fluid acetylcholinesterase or cholinesterase is reliable and the activity of the enzyme is stable. Low acetylcholinesterase or cholinesterase levels presenting in cerebrospinal fluid of a demented individual may confirm the clinical diagnosis of Alzheimer's disease or other organic dementia. A low activity of acetylcholinesterase or cholinesterase existing in cerebrospinal fluid of a non-demented individual may indicate a brain at risk, or that the person is in the preclinical stage of dementia. Recognition of the presence of the preclinical stage may be very beneficial for explaining the real meaning of the 'overlap' in the biochemistry and pathology between dementia and non-dementia, and also very important for prevention and treatment. Therefore, the strategy of prevention and of treatment should no longer be designed to inhibit acetylcholinesterase activity. In contrast, it should be designed to enhance the neuronal acetylcholinesterase activity or to delay the degeneration of brain acetylcholinesterase system.

Non-classical actions of cholinesterases: role in cellular differentiation, tumorigenesis and Alzheimer's disease

The cholinesterases are members of the serine hydrolase family, which utilize a serine residue at the active site. Acetylcholinesterase (AChE) is distinguished from butyrylcholinesterase (BChE) by its greater specificity for hydrolysing acetylcholine. The function of AChE at cholinergic synapses is to terminate cholinergic neurotransmission. However, AChE is expressed in tissues that are not directly innervated by cholinergic nerves. AChE and BChE are found in several types of haematopoietic cells. Transient expression of AChE in the brain during embryogenesis suggests that AChE may function in the regulation of neurite outgrowth. Overexpression of cholinesterases has also been correlated with tumorigenesis and abnormal megakaryocytopoiesis. Acetylcholine has been shown to influence cell proliferation and neurite outgrowth through nicotinic and muscarinic receptor-mediated mechanisms and thus, that the expression of AChE and BChE at non-synaptic sites may be associated with a cholinergic function. However, structural homologies between cholinesterases and adhesion proteins indicate that cholinesterases could also function as cell-cell or cell-substrate adhesion molecules. Abnormal expression of AChE and BChE has been detected around the amyloid plaques and neurofibrillary tangles in the brains of patients with Alzheimer's disease. The function of the cholinesterases in these regions of the Alzheimer brain is unknown, but this function is probably unrelated to cholinergic neurotransmission. The presence of abnormal cholinesterase expression in the Alzheimer brain has implications for the pathogenesis of Alzheimer's disease and for therapeutic strategies using cholinesterase inhibitors.

Neuropathology of thiamine deficiency: an update on the comparative analysis of human disorders and experimental models

This paper provides a re-examination of the neuroanatomical consequences of thiamine deficiency in light of more recent studies of human disorders and models of experimental thiamine deficiency. A major goal is to elucidate the relative roles of thiamine deficiency and chronic alcohol consumption in the pathogenesis of Wernicke-Korsakoff syndrome (WKS). Particular emphasis is placed on the role of thiamine deficiency in lesions to basal forebrain, raphe, locus coeruleus, white matter and cortex and their role in the cognitive and memory disturbances of human WKS and experimental models of thiamine deficiency.

Peptidergic transmission: from morphological correlates to functional implications

Like non-peptidergic transmitters, neuropeptides and their receptors display a wide distribution in specific cell types of the nervous system. The peptides are synthesized, typically as part of a larger precursor molecule, on the rough endoplasmic reticulum in the cell body. In the trans-Golgi network, they are sorted to the regulated secretory pathway, packaged into so-called large dense-core vesicles, and concentrated. Large dense-core vesicles are preferentially located at sites distant from active zones of synapses. Exocytosis may occur not only at synaptic specializations in axonal terminals but frequently also at nonsynaptic release sites throughout the neuron. Large dense-core vesicles are distinguished from small, clear synaptic vesicles, which contain "classical' transmitters, by their morphological appearance and, partially, their biochemical composition, the mode of stimulation required for release, the type of calcium channels involved in the exocytotic process, and the time course of recovery after stimulation. The frequently observed "diffuse' release of neuropeptides and their occurrence also in areas distant to release sites is paralleled by the existence of pronounced peptide-peptide receptor mismatches found at the light microscopic and ultrastructural level. Coexistence of neuropeptides with other peptidergic and non-peptidergic substances within the same neuron or even within the same vesicle has been established for numerous neuronal systems. In addition to exerting excitatory and inhibitory transmitter-like effects and modulating the release of other neuroactive substances in the nervous system, several neuropeptides are involved in the regulation of neuronal development.

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.

Triiodothyronine regulates somatostatin gene expression in cultured fetal rat cerebrocortical cells

The effect of triiodothyronine (T3) on somatostatin (SS) mRNA levels in cultured fetal rat cerebrocortical cells was studied. Two different experimental approaches were sought. They differed in the length of time in which cells were deprived of thyroid hormones prior to the addition of exogenous T3. When the cells were not deprived of thyroid hormones, T3 caused a dose-related decrease in SS mRNA content at all doses tested. However, when the cells were deprived of T3 for 24 h, a biphasic effect was observed. These findings suggest that T3 regulates SS gene expression in fetal cultured cerebrocortical cells.

Cerebrospinal fluid somatostatin concentrations in schizophrenia and schizoaffective disorder: the effects of antipsychotic treatment

The authors examined the effects of antipsychotic treatment on cerebrospinal fluid somatostatin like immunoreactivity (CSF SLI) in 14 schizophrenic and 3 schizoaffective patients. There was a modest but significant increase in CSF SLI in 13 out of the 14 schizophrenic patients. In addition, there was a significant positive correlation between duration of treatment and post-treatment CSF SLI concentrations. No differential response was noted in patients also treated with the anticholinergic benztropine.

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)

Peptide histidine methionine in cerebrospinal fluid of patients with senile dementia of the Alzheimer type

Immunoreactivities (IRs) of peptide histidine methionine (PHM) as well as somatostatin and vasoactive intestinal peptide (VIP) in the cerebrospinal fluid (CSF) were measured in patients with senile dementia of the Alzheimer type (SDAT) and age-matched control subjects. We found statistically significant reductions in the PHM-IR and somatostatin-IR levels in the CSF from patients with SDAT, as compared with those of the controls. However, the VIP-IR level in the CSF from SDAT was not different from that of the controls. These results suggest that selective degeneration of neurons containing somatostatin and PHM or the alteration in metabolism of PHM in the CSF might occur in SDAT.

Habenulo-interpeduncular descending pathways and their relationship to enkephalin- and somatostatin-immunoreactive neurons in the interpeduncular nucleus of human fetuses

The interpeduncular nucleus of six human fetuses aged 15 (one specimen), 26 (one specimen), 38 (one specimen) and 40 (three specimens) gestation weeks was studied by immunohistochemistry for enkephalin and somatostatin localization and immunohistochemistry coupled with silver staining. Enkephalin-positive and somatostatin-positive cells were detected, the former initially at 15 weeks gestation and the latter at 26 weeks gestation. They appeared to receive long afferents from the habenular region and projected short efferents to adjacent cells devoid of enkephalin and somatostatin positivity. We postulate that these enkephalin- and somatostatin-positive neurons function as modulatory interneurons in the habenulo-interpeduncular and related pathways.

CSF cholinesterase in early-onset and late-onset Alzheimer's disease and multi-infarct dementia of Chinese patients

Using Ellman spectrophotometric method we measured the total cholinesterase (ChE) activity in lumbar cerebrospinal fluid (CSF) of 13 persons without neurological disorder, 10 non-demented patients with cerebral infarcts, 17 patients with dementia of Alzheimer's type (DAT) (11 presenile, 6 senile cases), 10 patients with multi-infarct dementia (MID), 1 patient with Parkinson's disease associated with dementia. The ChE activity in CSF was significantly lower in the DAT group compared with age-matched control subjects (p < 0.001). This paper also analyses the possibility of using CSF ChE activity as a marker of DAT, and the relationships between its level of activity and the age of the patient at onset, stage of illness and severity of dementia as well as discrepancies in the data published so far. Previous work has shown that ChE activity in the brain tissue and CSF of MID is normal: therefore, if low ChE activity is found in the CSF of MID patients, as was obtained in 8 out of 10 cases in our series, the diagnosis of mixed dementia should be considered.

Somatostatin in the cerebrospinal fluid of schizophrenic patients before and after neuroleptic drug treatment

A radioimmunoassay procedure was used to determine levels of somatostatin-like immunoreactivity in cerebrospinal fluid obtained from 9 schizophrenic patients, 7 patients with other psychiatric disorders, and 10 nonpsychiatric surgical controls. There were no significant differences in mean somatostatin baseline levels between the schizophrenic, nonschizophrenic, and surgical patients. The concentration remained almost unaltered after 4 weeks of zuclopenthixol treatment in the schizophrenia group and following various neuroleptic, antidepressant, and anxiolytic medications in the nonschizophrenic patients despite a significant decrease of overt psychopathology assessed by the Brief Psychiatric Rating Scale.

Brain and cerebrospinal fluid cholinesterases in Alzheimer's disease, Parkinson's disease and aging. A critical review of clinical and experimental studies

Acetylcholinesterase (AChE), an enzyme responsible for the break-down of acetylcholine, is found both in cholinergic and non-cholinergic neurons in the central nervous system. In addition to its role in the catabolism of acetylcholine, AChE have other functions in brain, e.g. in the processing of peptides and proteins, and in the modulation of dopaminergic neurons in the brain stem. Several clinical and experimental studies have investigated AChE in brain and cerebrospinal fluid (CSF) in aging and dementia. The results suggest that brain AChE and its molecular forms show interesting changes in dementia and aging. However, CSF-AChE activity is not a very reliable or sensitive marker of the integrity and function of cholinergic neurons in the basal forebrain complex. Additional work is needed to clarify the role of AChE abnormality in the formation of pathology changes in patients with Alzheimer's disease.

Changes in acetylcholinesterase and butyrylcholinesterase in Alzheimer's disease resemble embryonic development--a study of molecular forms

The pattern of molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) separated by density gradient centrifugation was investigated in the brain and cerebrospinal fluid in Alzheimer's disease (AD), in human embryonic brain and in rat brain after experimental cholinergic deafferentation of the cerebral cortex. While a selective loss of the AChE G4 form was a rather constant finding in AD, a small but significant increase of G1 for both AChE and BChE was found in the most severely affected cases. Both in normal human brain and in AD a significant relationship could be established between the AChE G4/G1 ratio in different brain regions and the activity of choline acetyltransferase (ChAT). A similar decrease of the AChE G4 form as observed in AD can be induced in rat by experimental cholinergic deafferentation of the cerebral cortex. The increase in G1 of both AChE and BChE in different brain regions in AD is quantitatively related to the local density of neuritic plaques which are histochemically reactive for both enzymes. In human embryonic brain, a high abundance of G1 and a low G4/G1 ratio for both AChE and BChE was found resembling the pattern observed in AD. Furthermore, both in embryonic brain and in AD AChE shows no substrate inhibition which is a constant feature of the enzyme in the adult human brain. It is, therefore, concluded that the degeneration of the cholinergic cortical afferentation in AD as reflected by a decrease of AChE G4 is accompanied by the process of a neuritic sprouting response involved in plaque formation which is probably associated with the expression of a developmental form of the enzyme.

Cerebrospinal fluid norepinephrine, 3-methoxy-4-hydroxyphenylglycol and neuropeptide Y levels in Parkinson's disease, multiple system atrophy and dementia of the Alzheimer type

Neuropeptide Y, one of the most abundant polypeptides within the nervous system, is co-stored with catecholamines, especially norepinephrine (NE), thus suggesting its possible involvement in pathologies characterized by a noradrenergic impairment. In Parkinson's disease (PD), as well as in multiple system atrophy (MSA), a central noradrenergic deficit has been demonstrated, and in the dementia of Alzheimer type (DAT) an impaired noradrenergic transmission has been postulated. In this study we determined CSF NE and MHPG levels in 29 PD, 15 MSA, 22 DAT patients and in 36 controls, while CSF NPY-immunoreactivity (NPY-ir) levels were measured in 10 PD, 7 MSA, 10 DAT patients and 20 controls. PD, MSA, and DAT patients showed a significant reduction in CSF NPY-ir and NE levels compared with controls, while CSF MHPG levels resulted in a reduction in only the MSA group. Furthermore, an inverse correlation between either NE or MHPG levels and the duration of the orthostatic hypotension was found in MSA patients while for DAT patients the MHPG levels were directly correlated to the severity of cognitive impairment, and inversely to the duration of illness.

Amyloid beta protein precursors with kunitz-type inhibitor domains and acetylcholinesterase in cerebrospinal fluid from patients with dementia of the Alzheimer type

We used the ELISA to measure the concentration of amyloid protein precursor with Kunitz type trypsin inhibitor domains (APPI) in CSF of dementia of the Alzheimer type (DAT) and examined the correlation of APPI with acetylcholinesterase (AChE) and somatostatin (SRIF). We found the APPI concentration in CSF of DAT to be significantly elevated compared with that of multi-infarct dementia and controls. We could significantly correlate APPI with AChE, but not correlate APPI with SRIF. The present results suggest that measurement of CSF APPI levels may be useful for diagnosis of DAT and the change of APPI may closely be associated with abnormality of acetylcholine system in DAT that has been reported.

Concentrations of monoamines and their metabolites in the cerebrospinal fluid from patients with senile dementia of the Alzheimer type and vascular dementia of the Binswanger type

We measured the concentrations of total (conjugated and unconjugated) monoamines (dopamine, DA; norepinephrine, NE) and monoamine metabolites (homovanillic acid, HVA; 3-methoxy-4-hydroxyphenyleneglycol, MHPG; 5-hydroxyindoleacetic acid, 5-HIAA) in the cerebrospinal fluid (CSF), using HPLC-ECD in 11 patients with Alzheimer's disease (AD) or senile dementia of the Alzheimer type (SDAT), 17 patients with vascular dementia of the Binswanger type (VDBT), and 15 controls. In AD/SDAT, there was a significant decrease in the DA concentration and a significant increase in the MHPG concentration. The average NE concentration was not altered, but significantly increased with the progression of intellectual disability. There were no significant changes in HVA and 5-HIAA concentrations. Patients with VDBT showed a significant increase in the DA concentration and a significant decrease in HVA and 5-HIAA concentrations. The DA concentrations increased significantly with the progression of dementia and ventricular enlargement. These results indicate that the noradrenergic and dopaminergic system in particular are altered in AD/SDAT, while the dopaminergic and serotonergic systems are mainly involved in VDBT.

Neurochemical markers in the cerebrospinal fluid of patients with Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis and normal controls

Several neurotransmitter markers were investigated in the cerebrospinal fluid (CSF) from patients with Alzheimer's disease (AD) (n = 27), Parkinson's disease (PD) (n = 35) and ALS (n = 26) and from control subjects (n = 34) to compare the possible alterations in the biochemical profiles of these different neurodegenerative diseases. The main proportion of the patients represented an early phase of the illness at the time of the diagnosis. Correlations of the degree of dementia and the stage of the disease with CSF measures were evaluated. The CSF levels of somatostatin like-immunoreactivity (SLI) were significantly reduced in AD patients when compared with those of normals and ALS patients. The CSF concentrations of homovanillic acid (HVA) were significantly decreased for PD patients and the decrease focused on the non-demented patients. A trend of decreasing HVA values towards the most advanced stage of Parkinson's disease assessed by Webster's scale was also displayed. The content of 3-methoxy-4-hydroxyphenylglycol (MHPG) in the CSF was higher for ALS patients than for other groups. The lowest 5-hydroxy-indoleacetic acid (5HIAA) levels were observed in the PD group and the lowest acetylcholinesterase (AChE) activities were found in the PD patients with the most severe disease. Changes in CSF measures were too subtle to be beneficial for diagnostic purposes, but adequate for reflecting the different neurochemical profiles of these three degenerative neurological disorders.

Somatostatin in Alzheimer's disease and depression

Somatostatin (somatotropin release-inhibiting factor, SRIF) was originally discovered (1) during the purification of growth hormone-releasing factor from rat hypothalamus and was subsequently isolated and characterized (2) in 1972 from ovine hypothalamus. Since its initial characterization, SRIF has been shown to fulfill criteria for a neurotransmitter and to directly modulate neuronal activity as well as acting as an inhibitory factor regulating endocrine and exocrine secretion. Alterations in cerebrospinal fluid (CSF) concentrations of SRIF have been reported in several diseases exhibiting prominent cognitive dysfunction, including Alzheimer's disease (AD), major depression, Huntington's chorea, multiple sclerosis, schizophrenia and Parkinson's disease, while evidence for regional brain tissue concentration deficits in SRIF are more specific for AD. This mini-review will focus on the studies reporting alterations in CSF and postmortem tissue concentrations of SRIF in AD and depression.

Cerebrospinal fluid markers of Alzheimer's disease

OBJECTIVE

To review studies on cerebrospinal fluid (CSF) in patients with Alzheimer's disease (AD) in order to answer the question whether CSF contains a specific marker which can be used to support a clinical diagnosis of AD.

DATA SOURCES

Studies identified through an English-language literature search using MEDLINE (1966 to 1990) and a review of bibliographies of relevant articles.

STUDY SELECTION

All studies on CSF in AD patients were selected. Double publications on the same original data were not included. Otherwise, no particular selection was made.

DATA EXTRACTION

The diagnostic utility of more than 60 substances, including CSF measures related to classical neurotransmitters, (neuro)peptides, proteins, amino acids, purines, trace elements, and constituents of senile plaques and neurofibrillary tangles, is evaluated. Clinical epidemiological criteria for deciding on the usefulness of new diagnostic methods are emphasized in this analysis.

DATA SYNTHESIS

Concentrations of some CSF constituents are consistently found to be significantly changed in AD. However, overlap with data of control populations and methodological shortcomings in study design, limit the diagnostic value of all CSF measurements reviewed.

CONCLUSIONS

None of the CSF constituents studied so far can be used in support of the diagnosis of AD. However, increased knowledge concerning macromolecular abnormalities in amyloid containing plaques and neurofibrillary tangles makes the outlook for a diagnostic test for AD on CSF promising.

A longitudinal study of cerebrospinal fluid acetylcholinesterase in delirium: changes at the acute stage and at one-year followup

Cerebrospinal fluid acetylcholinesterase (CSF AChE) was determined for elderly delirious patients during the acute stage and after a 1-year followup, and the AChE levels were compared with those of age-equivalent controls. At the acute phase, the AChE levels of the delirious patients were in the same range as those of the control group, but during the followup, a slight declining trend was observed. These results do not unambiguously support the previously suggested role of cholinergic dysfunction in the pathogenesis of acute delirium, although the augmented striatal release of AChE in hyperkinetic and mixed delirium may mask the involvement of cholinergic neurons.

Reduced cerebrospinal fluid dynorphin A1-8 in Alzheimer's disease

Cerebrospinal fluid (CSF) measures of dynorphin A were compared in three groups. Alzheimer patients (n = 9), elderly depressives (n = 9), and age-matched normal controls (n = 9). The Alzheimer patients revealed a 40% decrease in CSF dynorphin compared with controls (36 +/- 15 versus 60 +/- 21 pg/ml, p less than 0.05). In contrast, other peptide measures [Neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), and galanin] remained unchanged across groups. This finding was further supported when an additional 20 Alzheimer patients with similar clinical backgrounds also showed reduced CSF dynorphin (37 +/- 13 pg/ml). CSF dynorphin did not correlate significantly with clinical variables or other CSF measures of monoamine metabolites [i.e., 3-methoxy-4-hydroxyphenylglycol (MHPG), 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA)]. Given the previous report of increased kappa binding of Alzheimer brains at autopsy, the authors speculate about a possible up-regulation of opiate receptors in Alzheimer's disease and suggest ways to test this hypothesis in vivo.

Cerebrospinal fluid acetylcholinesterase in patients with dementia associated with schizophrenia or chronic alcoholism

Cerebrospinal fluid (CSF) acetylcholinesterase (AChE) was determined for 11 chronic schizophrenic patients with dementia, 9 patients with dementia associated with alcoholism and 8 age-equivalent control subjects. The AChE levels in both patient groups were unrelated to the degree of cognitive decline and they were in the same range as in the control group. In schizophrenic patients no relationship was found between CSF AChE and the severity of psychotic symptoms. Our results suggest that dementia may occur in these patient groups without CSF AChE involvement.

Somatostatin cerebrospinal fluid levels in dementia

Somatostatin levels were measured in cerebrospinal fluid of patients with Alzheimer's disease, multi-infarct dementia and normal pressure hydrocephalus and compared with levels from a normal control group. All pathological groups showed a statistically significant decrease of somatostatin with respect to the control group, but no significant differences were found amongst them. A negative correlation was found between the Mini Mental State Test and the somatostatin levels in Alzheimer's disease patients but not in the other groups. Our results confirm that the lower levels of somatostatin in cerebrospinal fluid are not specific to Alzheimer's disease and indicate that the decrease found in all the groups is probably the result of neuronal destruction or damage in the diseases examined.

Monoamines and related metabolite levels in the cerebrospinal fluid of patients with dementia of Alzheimer type. Influence of treatment with L-deprenyl

An impairment of the monoaminergic systems has frequently been reported for Alzheimer's disease (AD) as well as an overactivity of cerebral monoamineoxidase B (MAO-B). L-deprenyl (LD), a selective and irreversible MAO-B inhibitor, has recently been proposed for the treatment of AD. The cerebrospinal fluid (CSF) levels of norepinephrine (NE), epinephrine (E), dopamine (DA), 3-methoxy-4-hydroxyphenylglycol (MHPG), 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) were studied in 14 patients suffering from dementia of Alzheimer type (DAT) and in 14 controls. A three-month double-blind study comparing LD with placebo was carried out, in the DAT group, and the influence of the treatment on neurotransmitter levels and cognitive performance was evaluated. The basal study revealed a significant reduction in CSF NE and HVA levels in DAT patients when compared with controls; the treatment with LD determined a significant decrease in HVA levels only and, as to neuropsychological investigation, a global amelioration of cognitive performances.

Neuroendocrine dysfunction in psychotic disorders (excluding ACTH)

Neuropeptide and neuroendocrine studies in the two major 'functional' psychotic illnesses have been reviewed. Changes in schizophrenia suggest both central dopamine dysfunction and hypothalamic, and perhaps, limbic pathology. In affective disorders, disruption of rhythmic neuroendocrine control seems to be evident, possibly mediated by either abnormal 5-hydroxytryptamine receptor function, non-specific hypothalamic derangement, or both. It is conceivable that some neuroendocrine changes in depression are trait phenomena which may be markers or mechanisms of vulnerability. The interaction of neuropeptide function and neuroendocrine state in psychotic illness is likely to be the focus of intensive future research.

Decreased somatostatin-like immunoreactivity in the cerebrospinal fluid of chronic schizophrenic patients with cognitive impairment

The level of cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for 11 chronic schizophrenic patients with moderate cognitive impairment and for 8 controls. The CSF SLI was significantly reduced (37%) in schizophrenic patients, but this decrease did not correlate with the degree of cognitive decline measured by the Mini-Mental State Examination, with psychotic symptoms estimated by the Brief Psychiatric Rating Scale, or with the neuroleptic dose. Although a reducing effect of long-term neuroleptic treatment cannot be totally excluded, the present study suggests that the CSF SLI level is decreased in cognitively impaired schizophrenic patients, as in many other disorders with cognitive impairment.

Endocrine responses to growth hormone releasing hormone and corticotropin releasing hormone in early-onset Alzheimer's disease

In a study of the hypothalamic-pituitary-somatotropic (HPS) and the hypothalamic-pituitary-adrenal (HPA) systems in early-onset Alzheimer's disease (AD), 10 drug-naive patients and matched controls were given 50 micrograms growth hormone releasing hormone (GHRH) at 9 a.m. and 100 micrograms corticotropin releasing hormone (CRH) at 6 p.m. as an i.v. bolus dose. Compared with controls, patients with AD showed attenuated GHRH-induced growth hormone (GH) responses and decreased adrenocorticotropic hormone (ACTH) but normal cortisol secretion following CRH. GH responses to GHRH were negatively correlated with the plasma insulin-like growth factor (IGF-I) concentrations and the severity of dementia. A positive correlation was found between GHRH-evoked GH release and ACTH responses to CRH. The results suggest a pathological process at the level of the pituitary or the hypothalamus, possibly involving a cholinergic, monoaminergic, or peptidergic imbalance in AD, and support the view that altered HPS and HPA secretory dynamics in AD are related to the underlying brain dysfunction.

Cerebrospinal fluid levels of somatostatin, corticotropin-releasing hormone and corticotropin in alcoholism

Reduced brain and cerebrospinal fluid (CSF) levels of somatostatin, corticotropin-releasing hormone (CRH) and corticotropin (ACTH) have been reported among neuropsychiatric patients with cognitive dysfunction. Alcoholism is a disorder in which associated neuropsychiatric disorders occur. Therefore, we compared CSF levels of somatostatin, CRH and ACTH in alcoholics (n = 100) and normal controls (n = 30). There were no significant differences between the groups in concentrations of the 3 peptides. Moreover, there were no significant correlations between concentrations of the peptides in CSF and computed tomographic measures of the size of brain ventricles. There were, however, significant correlations between CSF concentrations of CRH and ACTH and between CSF concentrations of CRH and somatostatin in both the alcoholic and control groups.

The effects of somatostatin and somatostatin antiserum on the retention of passive avoidance behavior after neofrontal decortication in rats

Rats were tested for passive avoidance behavior in a one-trial step-through learning paradigm. After the learning trial, the animals underwent neofrontal decortication or sham operation. On the 8th day after operation, the lesioned or sham-operated rats received intracerebroventricular (ICV) injections of somatostatin (SST; 4 micrograms/2 microliters) or somatostatin antiserum (SST-AB; 2 microliters) 1 hr before the retention test. Decortication alone decreased the latency in comparison to that in the sham-operated group, and ICV treatment did not influence this impairment. After treatment with SST-AB the latency decreased, indicating that endogenous SST may play a role in the maintenance of normal memory processes.

Vasopressin, prolactin and growth hormone in Alzheimer's disease: their evaluation after metoclopramide stimulation

Recent studies have shown that there is a relationship between an alteration of central neurotransmitters and the modification of some biohumoral parameters in Alzheimer's Disease (AD). In this study the authors evaluated, after metoclopramide (MTC) stimulation, the concentration curve of vasopressin (AVP), prolactin (PRL) and growth hormone (HGH) in the plasma of 34 subjects (20 males and 14 females, mean age 70.5+/-6.9 years; 17 were AD patients, the others constituted the control group). MTC increased AVP serum concentration in healthy (P <0.001), but not in AD patients. This result seemed to be due to the lack of 'procholinergic' action of the drug in the AD patients probably due to an alteration in their cholinergic pathways. The PRL response to MTC was reduced only in the AD female group (P <0.005), suggesting an alteration in dopaminergic control. Lastly, the HGH response in AD did not differ in the two groups, neither in basal conditions, nor after MTC stimulation. The absence of HGH response both in AD and in healthy subjects, demonstrated the ineffectiveness of MTC stimulation. We can conclude that AVP and PRL responses to MTC stimulation efficiently separated the two groups (AD and controls); the former test showing a higher discriminant power than the latter.