Increased levels of neuronal thread protein in cerebrospinal fluid of patients with Alzheimer's disease

Alzheimer-Associated Neuronal Thread Protein: Research Course and Prospects for the Future

Alzheimer's disease (AD) is the leading cause of dementia. With aging societies, the prevalence of AD is increasing dramatically worldwide. The onset of AD is often not identified, and currently no available treatments are capable of stopping the disease process and its effect on cognitive decline. Thus, well-validated biomarkers of the preclinical stages of AD are needed. Alzheimer-associated neuronal thread protein (AD7c-NTP) is a member of the neuronal thread protein family and has a molecular weight of approximately 41 kD. AD7c-NTP has been identified as a biomarker for its specifically elevated levels in putative brain domains, cerebrospinal fluid (CSF), and the urine of AD and mild cognitive impairment (MCI) patients. Since the urine test is non-invasive, easy to perform, and patients accept it more easily than other methods, the urinary AD7c-NTP concentration has been recommended as a practical diagnostic tool for diagnosing AD and MCI. AD7c-NTP has undergone nearly 25 years of research course from its initial discovery to pathological verification, multi-center clinical evaluation, improvement of detection methods, epidemiological investigation, and combined application with other biomarkers. However, as a fluid biomarker, AD7c-NTP can be detected in urine instead of the traditional biomarker sources-CSF or blood, which has made the use of AD7c-NTP as a biomarker controversial. In this article, we review the research course of AD7c-NTP and suggest directions for future research.

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Diagnostic cerebrospinal fluid biomarkers for Parkinson's disease: a pathogenetically based approach

The inaccuracy of the early diagnosis of Parkinson's disease (PD) has been a major incentive for studies aimed at the identification of biomarkers. Brain-derived cerebrospinal fluid (CSF) proteins are potential biomarkers considering the major role that proteins play in PD pathogenesis. In this review, we discuss the current hypotheses about the pathogenesis of PD and identify the most promising candidate biomarkers among the CSF proteins studied so far. The list of potential markers includes proteins involved in various pathogenetic processes, such as oxidative stress and protein aggregation. This list will undoubtedly grow in the near future by application of CSF proteomics and subsequent validation of identified proteins. Probably a single biomarker will not suffice to reach high sensitivity and specificity, because PD is pathogenetically heterogeneous and shares etiological factors with other neurodegenerative diseases. Furthermore, identified candidate biomarkers will have to be thoroughly validated before they can be implemented as diagnostic aids.

Practical utility of urinary assay in the diagnosis of Alzheimer's disease: AlzheimAlert

Urinary assay (Alzheimer's disease reaction titer [ADRT]) adds significant information in the diagnosis of Alzheimer's disease (AD), particularly for the nonspecialist. Clinical studies of ADRT in series of AD and non-AD patients have found sensitivity of 89-92.3%, specificity of 90-96.8%, positive predictive value (PPV) of 94.8-97.4% and negative predictive value (NPV) of 78.9-91.8%. The added information from the improvements of PPV and NPV are particularly helpful for the nonspecialist in the community. As a laboratory assay that requires a first-morning noncontaminated sample, ADRT is noninvasive, convenient and safe. ADRT is based on reagents derived from human AD brain cDNA. The pathophysiological roles of these genetic fragments and reagents are still under investigation. ADRT should have a positive impact on primary-care AD clinical practice.

Alzheimer's disease and mild cognitive impairment

As our society ages, age-related diseases assume increasing prominence as both personal and public health concerns. Disorders of cognition are particularly important in both regards, and Alzheimer's disease is by far the most common cause of dementia of aging. In 2000, the prevalence of Alzheimer's disease in the United States was estimated to be 4.5 million individuals, and this number has been projected to increase to 14 million by 2050. Although not an inevitable consequence of aging, these numbers speak to the dramatic scope of its impact. This article focuses on Alzheimer's disease and the milder degrees of cognitive impairment that may precede the clinical diagnosis of probable Alzheimer's disease, such as mild cognitive impairment.

Fibrinogen gamma-A chain precursor in CSF: a candidate biomarker for Alzheimer's disease

BACKGROUND

Cerebrospinal fluid (CSF) may be valuable for exploring protein markers for the diagnosis of Alzheimer's disease (AD). The prospect of early detection and treatment, to slow progression, holds hope for aging populations with increased average lifespan. The aim of the present study was to investigate candidate CSF biological markers in patients with mild cognitive impairment (MCI) and AD and compare them with age-matched normal control subjects.

METHODS

We applied proteomics approaches to analyze CSF samples derived from 27 patients with AD, 3 subjects with MCI and 30 controls. The AD group was subdivided into three groups by clinical severity according to clinical dementia rating (CDR), a well known clinical scale for dementia.

RESULTS

We demonstrated an elevated level of fibrinogen gamma-A chain precursor protein in CSF from patients with mild cognitive impairment and AD compared to the age-matched normal subjects. Moreover, its expression was more prominent in the AD group than in the MCI and correlated with disease severity and progression. In contrast, fibrinogen gamma-A chain precursor protein was detected very low in the age-matched normal group.

CONCLUSION

These findings suggest that the CSF level of fibrinogen gamma-A chain precursor may be a candidate biomarker for AD.

Consensus paper of the WFSBP Task Force on Biological Markers of Dementia: the role of CSF and blood analysis in the early and differential diagnosis of dementia

Aging of population, and increasing life expectancy result in an increasing number of patients with dementia. This symptom can be a part of a completely curable disease of the central nervous system (e.g, neuroinflammation), or a disease currently considered irreversible (e.g, Alzheimer's disease, AD). In the latter case, several potentially successful treatment approaches are being tested now, demanding reasonable standards of pre-mortem diagnosis. Cerebrospinal fluid and serum analysis (CSF/serum analysis), whereas routinely performed in neuroinflammatory diseases, still requires standardization to be used as an aid to the clinically based diagnosis of AD. Several AD-related CSF parameters (total tau, phosphorylated forms of tau, Abeta peptides, ApoE genotype, p97, etc.) tested separately or in a combination provide sensitivity and specificity in the range of 85%, the figure commonly expected from a good diagnostic tool. In this review, recently published reports regarding progress in neurochemical pre-mortem diagnosis of dementias are discussed with a focus on an early and differential diagnosis of AD. Novel perspectives offered by recently introduced technologies, e.g, fluorescence correlation spectroscopy (FCS) and surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) are briefly discussed.

Cerebrospinal fluid protein biomarkers for Alzheimer's disease

The introduction of acetylcholine esterase (AChE) inhibitors as a symptomatic treatment of Alzheimer's disease (AD) has made patients seek medical advice at an earlier stage of the disease. This has highlighted the importance of diagnostic markers for early AD. However, there is no clinical method to determine which of the patients with mild cognitive impairment (MCI) will progress to AD with dementia, and which have a benign form of MCI without progression. In this paper, the performance of cerebrospinal fluid (CSF) protein biomarkers for AD is reviewed. The diagnostic performance of the three biomarkers, total tau, phospho-tau, and the 42 amino acid form of beta-amyloid have been evaluated in numerous studies and their ability to identify incipient AD in MCI cases has also been studied. Some candidate AD biomarkers including ubiquitin, neurofilament proteins, growth-associated protein 43 (neuromodulin), and neuronal thread protein (AD7c) show interesting results but have been less extensively studied. It is concluded that CSF biomarkers may have clinical utility in the differentiation between AD and several important differential diagnoses, including normal aging, depression, alcohol dementia, and Parkinson's disease, and also in the identification of Creutzfeldt-Jakob disease in cases with rapidly progressive dementia. Early diagnosis of AD is not only of importance to be able to initiate symptomatic treatment with AChE inhibitors, but will be the basis for initiation of treatment with drugs aimed at slowing down or arresting the degenerative process, such as gamma-secretase inhibitors, if these prove to affect AD pathology and to have a clinical effect.

Tau protein concentrations in cerebrospinal fluid of patients with multiple sclerosis

FUNDAMENTALS AND OBJECTIVE: Multiple sclerosis (MS) is the prototype of demyelinating disease, but recently, it has been shown that the existence of axonal lesions contribute to irreversible central nervous system damage in this disease. Tau proteins are considered to be important for maintaining the stability of axonal microtubules involved in the mediation of fast axonal transport of synaptic constituents. There have been reports of increased cerebrospinal fluid (CSF) tau concentrations in patients with MS, and it has been suggested that this could be a marker of axonal damage. The objective of the present study was to elucidate whether CSF tau levels could be a marker of MS activity.

PATIENT AND METHODS

We measured tau concentrations in the CSF of 20 patients with MS (nine in the first, seven in the second, one in the fourth exacerbation, and three patients with chronic progressive course) and 32 age- and sex-matched controls, using a specific enzyme-linked immunosorbent assay method.

RESULTS

The CSF tau concentrations of patients with MS did not differ from those of controls, and they were not correlated with age at onset and duration of the disease.

CONCLUSION

CSF tau concentrations are not a marker of MS activity.

An unusually glycosylated form of acetylcholinesterase is a CSF biomarker for Alzheimer's disease

The identification of a biochemical marker of Alzheimer's disease (AD) is a major research aim of many groups. Abnormal levels of tau and Abeta have been identified in the cerebrospinal fluid (CSF) of AD patients, although the sensitivity and specificity of the changes in these two biomarkers alone is not sufficient to be of diagnostic value. Recently, our group has identified an abnormality in the glycosylation of acetylcholinesterase (AChE). The increase in this glycoform of AChE is very specific for Alzheimer's disease and is not seen in many other neurological diseases including other dementias.

Practice parameter: diagnosis of dementia (an evidence-based review). Report of the Quality Standards Subcommittee of the American Academy of Neurology

OBJECTIVE

To update the 1994 practice parameter for the diagnosis of dementia in the elderly.

BACKGROUND

The AAN previously published a practice parameter on dementia in 1994. New research and clinical developments warrant an update of some aspects of diagnosis.

METHODS

Studies published in English from 1985 through 1999 were identified that addressed four questions: 1) Are the current criteria for the diagnosis of dementia reliable? 2) Are the current diagnostic criteria able to establish a diagnosis for the prevalent dementias in the elderly? 3) Do laboratory tests improve the accuracy of the clinical diagnosis of dementing illness? 4) What comorbidities should be evaluated in elderly patients undergoing an initial assessment for dementia?

RECOMMENDATIONS

Based on evidence in the literature, the following recommendations are made. 1) The DSM-III-R definition of dementia is reliable and should be used (Guideline). 2) The National Institute of Neurologic, Communicative Disorders and Stroke--AD and Related Disorders Association (NINCDS-ADRDA) or the Diagnostic and Statistical Manual, 3rd edition, revised (DSM-IIIR) diagnostic criteria for AD and clinical criteria for Creutzfeldt--Jakob disease (CJD) have sufficient reliability and validity and should be used (Guideline). Diagnostic criteria for vascular dementia, dementia with Lewy bodies, and frontotemporal dementia may be of use in clinical practice (Option) but have imperfect reliability and validity. 3) Structural neuroimaging with either a noncontrast CT or MR scan in the initial evaluation of patients with dementia is appropriate. Because of insufficient data on validity, no other imaging procedure is recommended (Guideline). There are currently no genetic markers recommended for routine diagnostic purposes (Guideline). The CSF 14-3-3 protein is useful for confirming or rejecting the diagnosis of CJD (Guideline). 4) Screening for depression, B(12) deficiency, and hypothyroidism should be performed (Guideline). Screening for syphilis in patients with dementia is not justified unless clinical suspicion for neurosyphilis is present (Guideline).

CONCLUSIONS

Diagnostic criteria for dementia have improved since the 1994 practice parameter. Further research is needed to improve clinical definitions of dementia and its subtypes, as well as to determine the utility of various instruments of neuroimaging, biomarkers, and genetic testing in increasing diagnostic accuracy.

Human kallikrein 6 as a biomarker of alzheimer's disease

OBJECTIVES

Alzheimer's disease (AD) is a major cause of dementia in the elderly. It is generally difficult to diagnose accurately early AD. A few biomarkers, including tau protein and amyloid beta-42, are now used as aids for diagnosis and monitoring of AD. Our aim was to examine the possible use of cerebrospinal fluid, blood and tissue, and human kallikrein 6 (hK6) concentration as a marker of AD.

METHODS

We have used a highly sensitive and specific immunofluorometric procedure for measuring hK6. We measured hK6 in tissue extracts from AD brain or normal individuals, in cerebrospinal fluids of AD patients or normals and in whole blood of AD patients and normals and compared the findings. We have used ten pairs of AD/normal controls in all cases.

RESULTS

We found that hK6 concentration is tissue extracts from AD brain were approximately twofold lower than extracts from normal controls. Further, we found that cerebrospinal fluid hK6 concentration is approximately a threefold increase, in comparison to cerebrospinal fluid controls (p = 0.001). We have also found that the whole blood hK6 concentration in AD patients is about ten times higher than hK6 concentration in normal controls (p = 0.002). We have immunohistochemically localized the expression of hK6 in epithelial cells of the chorioid plexus.

CONCLUSIONS

This is the first report describing significant elevations of cerebrospinal fluid and plasma and whole blood hK6 concentration in AD patients, in comparison to controls. These data suggest that hK6 may constitute a new biomarker for diagnosis and monitoring of AD.

Alzheimer's disease

This article reviews the clinical and neuropathological features of Alzheimer's disease, its known genetic and non-genetic risk factors, procedures used to make the diagnosis and rule out other reversible and non-reversible forms of dementia, and the treatment strategies used to help patients and their families cope with the problem. In addition, it considers how neuroimaging techniques promise to characterize the brain changes which precede the onset of cognitive impairment in persons at risk for Alzheimer's disease and identify treatments to prevent the onset of dementia.

Biological markers for the diagnosis of Alzheimer's disease

A diagnostic test for Alzheimer's disease (AD) based on biochemical markers in the cerebrospinal fluid can help improve diagnostic accuracy, which currently is approximately 90%, leaving every tenth AD patient undiagnosed or falsely diagnosed as having the disease. From all biochemical abnormalities described in AD patients, those related to the hallmark neuropathologic lesions, deposition of amyloid and formation of paired helical filaments mainly consisting of abnormally phosphorylated tau protein, are the most promising and the best documented, even though other markers bear some potential and remain to be further studied. Determining an increase of tau and a reduction of A beta 42 bears satisfactory, even though not absolute specificity for AD and represents a true aid for clinicians in diagnosing AD during the patients lifetime. It remains open if these markers will be helpful for the most challenging goal, diagnosing AD in the preclinical phase, when, according to morphological data, high amounts of these pathological proteins are already deposited in the brain tissue.

Neuronal thread protein gene modulation with cerebral infarction

Neuronal thread proteins (NTP) are a family of phosphoproteins expressed during neuritic sprouting. The 15 to 18 kD NTP cluster is associated with development and neuronal differentiation, whereas the 21 kD and 39 to 42 kD species are overexpressed in Alzheimer's disease, correlating with neurodegenerative sprouting and synaptic disconnection. Empirical observations suggested that NTP might also be modulated with central nervous system injury and stroke. In this study of both human and experimental (rat) focal cerebral infarcts, in situ hybridization and immunocytochemical staining revealed NTP gene expression up-regulated in perifocal neurons. These findings were confirmed by quantitative Northern and Western blot analyses. Moreover, Western blot analysis demonstrated selectively increased expression of the 15 to 18 kD NTP species during the acute, subacute, and healing phases of cerebral infarction in both humans and experimental animals, corresponding with the expected period of neuronal repair. These results suggest an additional role for the 15 to 18 kD NTP species in neuritic sprouting required for neuronal regeneration after injury in the mature central nervous system.

Amyloid beta protein 42(43) in cerebrospinal fluid of patients with Alzheimer's disease

To investigate the pathomechanism of amyloid beta protein (A beta) deposition in brains with Alzheimer's disease (AD), cerebrospinal fluid (CSF) levels of A beta species (CSF-A beta) with different carboxy termini, i.e. A betaX-40 and A betaX-42(43) as well as A beta1-40 and A beta1-42(43), were measured in patients with AD and age-matched controls without dementia (CTR) using sandwich enzyme-linked immunosorbent assays (ELISAs). The present study revealed that both CSF-A betaX-42(43) and A beta1-42(43) levels were significantly lower in the AD patients (P<0.005) than in the CTR group, whereas neither CSF-A betaX-40 nor CSF-A beta1-40 levels showed any differences between the two groups. In addition, although there was no difference between the ratios of A betaX-40 to A beta1-40 in the AD and CTR groups, the ratios of A betaX-42(43) to A beta1-42(43) were increased in the AD group compared with those in the CTR group (P<0.05). Therefore, it can be assumed that the ratios of amino terminal truncations and/or modifications of CSF-A beta42(43) with carboxy termini ending at residue 42(43) were more increased in the AD group than in the CTR group. Increased adsorption of A beta42(43) to A beta deposition in AD brains, decreased secretion of A beta42(43) to CSF and/or increased clearance of A beta42(43) from CSF might explain the diminished levels of A beta42(43) in the CSF of AD patients. In addition, CSF-A beta42(43) could reflect increased amino terminal truncations and/or modifications of A beta42(43) in AD brains.

Modulation of neuronal thread protein expression with neuritic sprouting: relevance to Alzheimer's disease

Widespread proliferation of dystrophic neurites in the cerebral cortex represents an important neuroanatomical correlate of dementia in Alzheimer's disease (AD). Increased CNS expression of the 21-kDa neuronal thread protein (NTP) species is also correlated with dementia in AD. Pilot in vitro experiments provided evidence that high-level NTP expression might be linked to neuritic growth. The present study examines retinoic acid (RA) modulation of NTP expression during neurite outgrowth and neuronal differentiation in SH-Sy5y neuroblastoma and PNET2 CNS-derived cells. In both cell lines, RA-induced neuronal differentiation resulted in increased synthesis, expression, and phosphorylation of several NTP species, with high steady-state levels and stepwise hyper-phosphorylation of 21-kDa NTP molecules. With neurite outgrowth, NTP molecules were translocated from the perikarya to long, slender, unbranched cell processes (axons) and growth cones. RA-mediated changes in NTP expression were independent of DNA synthesis. The findings suggest that high-level expression of 21-kDa, and closely related phosphorylated NTP molecules correlates with neuritic growth. Therefore, over-expression of 21-kDa NTP molecules in AD probably reflects the widespread cortical neuritic sprouting associated with dementia. In view of the rapid phosphorylation and cell process translocation of NTP that occurs during neurite outgrowth in vitro, the accumulation of NTP in AD cortical neuronal perikarya suggests a further problem related to post-translational processing and transport of NTP molecules in AD neurodegeneration.

Developmental patterns of neuronal thread protein gene expression in Down syndrome

Neuronal thread proteins (NTP) are a group of immunologically related molecules expressed in brain and neuroectodermal tumor cell lines. NTP gene expression is up-regulated and NTP molecules accumulate in Alzheimer's disease (AD) brains, pathological states associated with regenerative neuritic sprouting, and during brain development. To investigate the role of NTP over-expression in AD, we examined NTP immunoreactivity in brains from differently aged individuals with Down syndrome, since patients with Down syndrome nearly always develop AD neuropathology and dementia. Using SMI monoclonal antibodies to neurofilament protein, we detected age-associated increases in neurofilament immunoreactive (SMI-positive) neurites in Layers I and II of the cerebral cortex beginning at 1 year of age, followed by SMI-positive neurofibrillary tangles beginning at age 5 years, and then SMI-positive plaques beginning in the third decade. Increased NTP immunoreactivity in Down syndrome brains began in the second decade, prior to establishment of widespread AD neurodegeneration (Down syndrome + AD), and at an age when low-level or absent NTP expression was observed in control brains. Analysis of SDS and Triton X-100-treated histological sections and tissue extracts demonstrated that a largely insoluble, denaturation-resistant form of NTP accumulates in both Down syndrome + AD and AD brains. The findings provide further evidence that abnormal NTP expression and accumulation in brain may be an early marker of AD neurodegeneration in Down syndrome.

Ethanol inhibits insulin receptor substrate-1 tyrosine phosphorylation and insulin-stimulated neuronal thread protein gene expression

Neuronal thread proteins (NTPs) are molecules that accumulate in the brains of patients with Alzheimer's disease, and may play a key role in both normal and neurodegenerative neuritic sprouting. In this investigation we determined whether NTP expression is up-regulated by insulin, an important neurotrophic factor that stimulates differentiation-associated neurite outgrowth, and studied the effects of ethanol, a known inhibitor of growth factor receptor tyrosine phosphorylation, on NTP expression and insulin-mediated signal transduction cascade in neuronal [primitive neuroectodermal tumour cell line 2; (PNET2)] cells. PNET2 cells were treated with 50 m-units/ml insulin in the presence or absence of 100 mM ethanol for 0.2-96 h, and cell proliferation and expression of NTP molecules were investigated by metabolic labelling, immunoprecipitation and immunohistochemical staining. Insulin stimulation resulted in an immediate increase in the levels of three (38, 18 and 15 kDa) of five NTP species (the others were of 26 and 21 kDa), followed by a decline in expression within 120 min; however, studies performed up to 96 h of culture demonstrated up-regulation by insulin of all five NTP species. Ethanol either abolished or severely muted the short- and long-term insulin-mediated upregulation of NTP expression, and substantially reduced insulin-mediated neuronal differentiation. The effects of ethanol on NTP gene expression were associated with impaired insulin-mediated tyrosine phosphorylation of both the insulin receptor beta subunit and the insulin receptor substrate-1 (IRS-1), resulting in decreased association of phosphatidylinositol 3-kinase with IRS-1. The findings suggest that ethanol may inhibit NTP expression associated with central nervous system neuronal differentiation by uncoupling the IRS-1-mediated insulin signal transduction pathway.

Cerebrospinal fluid neuropeptides in Alzheimer's disease and vascular dementia

Cerebrospinal fluid (CSF) levels of several neuropeptides have been suggested as candidate markers in neurodegenerative disorders. We have examined the levels of corticotropin-releasing hormone (CRH), beta-endorphine (BEND), delta sleep-inducing peptide (DSIP), somatostatin (SRIF), and neuropeptide Y (NPY) in CSF samples obtained under highly standardized conditions from healthy aged controls and from patients suffering from Alzheimer's disease (AD) or vascular dementia (VAD). The influence of some potentially confounding factors was evaluated. CRH and BEND were markedly decreased in both AD and VAD patients, and BEND levels correlated negatively with degree of dementia within the patient population. SRIF was decreased in both AD and VAD patients. DSIP was slightly increased in AD, but not in VAD. NPY did not differ between groups. For none of the peptides did CSF concentrations correlate significantly with duration of illness, nor, with the exception of BEND, with its degree. Present data do not support the hypothesis that specific neuropeptide changes occur in different neurodegenerative disorders, but are in agreement with previous reports suggesting that neuropeptide systems are differentially affected by neurodegeneration.

Clinical classification of dementias

The diagnosis of dementia disorders can be made in several steps. The symptomatology, severity and course of the illness must be considered. Memory disturbances must be present. Ante-mortem classification of dementias is based on known or assumed etiology. The final step is the post-mortem diagnosis. Of the primary dementias, Alzheimer-type dementia is the most important group. Accumulating data indicate that this form can be divided into subgroups. The concept of multi-infarct dementia (MID) should not be used synonymously with vascular dementia, which is a broader concept. Vascular dementias can also be divided into subgroups. Dementia is an advanced stage of a brain disorder. It seems important to identify brain disorders before they have reached the advanced level of dementia. A name for such disorders is dysmentia.

Insulin-induced differentiation and modulation of neuronal thread protein expression in primitive neuroectodermal tumor cells is linked to phosphorylation of insulin receptor substrate-1

Neuronal thread proteins (NTPs) are a family of developmentally regulated molecules expressed in central nervous system (CNS) neurons and primitive neuroectodermal tumor (PNET) cell lines. NTP gene expression is modulated with DNA synthesis, neuritic sprouting, and neuronal differentiation. The present study explores the mechanism of insulin modulation of NTP gene expression during neuronal differentiation using PNET cell lines of CNS origin. PNET2 cells underwent neuronal differentiation with neurite outgrowth coupled with transient up-regulation of several species of NTP. In contrast, PNET1 cells failed to differentiate in response to insulin stimulation, although insulin receptors were more abundant than in PNET2 cells. Analysis of the insulin-mediated signal transduction pathway demonstrated that the lack of insulin responsiveness in PNET1 cells was primarily caused by impaired insulin-mediated tyrosyl phosphorylation of the insulin receptor substrate-1 (IRS-1). Correspondingly, the association between phosphatidyl-inositol 3 (PI3) kinase and phosphorylated IRS-1 was reduced in PNET1 compared with PNET2 cells. In contrast, the levels of IRS-1 protein were similar in PNET1 and PNET2 cells, and expression of the insulin receptor beta subunit (Ir beta) and insulin-mediated tyrosyl phosphorylation of the Ir beta were greater in PNET1 than PNET2 cells. The findings suggest that insulin effected neuronal differentiation and modulation of NTP gene expression in PNET cells utilizes a signal transduction cascade that requires tyrosyl phosphorylation of IRS-1.

Nerve growth factor and Alzheimer's disease

Nerve growth factor (NGF) is a well-characterized protein that exerts pharmacological effects on a group of cholinergic neurons known to atrophy in Alzheimer's disease (AD). Considerable evidence from animal studies suggests that NGF may be useful in reversing, halting, or at least slowing the progression of AD-related cholinergic basal forebrain atrophy, perhaps even attenuating the cognitive deficit associated with the disorder. However, many questions remain concerning the role of NGF in AD. Levels of the low-affinity receptor for NGF appear to be at least stable in AD basal forebrain, and the recent finding of AD-related increases in cortical NGF brings into question whether endogenous NGF levels are related to the observed cholinergic atrophy and whether additional NGF will be useful in treating this disorder. Evidence regarding the localization of NGF within the central nervous system and its presumed role in maintaining basal forebrain cholinergic neurons is summarized, followed by a synopsis of the relevant aspects of AD neuropathology. The available data regarding levels of NGF and its receptor in the AD brain, as well as potential roles for NGF in the pathogenesis and treatment of AD, are also reviewed. NGF and its low affinity receptor are abundantly present within the AD brain, although this does not rule out an NGF-related mechanism in the degeneration of basal forebrain neurons, nor does it eliminate the possibility that exogenous NGF may be successfully used to treat AD. Further studies of the degree and distribution of NGF within the human brain in normal aging and in AD, and of the possible relationship between target NGF levels and the status of basal forebrain neurons in vivo, are necessary before engaging in clinical trials.

Alzheimer disease: correlation of cerebro-spinal fluid and brain ubiquitin levels

Neurofibrillary degeneration is one of the histopathological hallmarks of Alzheimer disease (AD). Previous studies have shown an association of ubiquitin with the cytoskeletal protein pathology in AD. In the present study, we report (i) the measurement of ubiquitin levels in cerebrospinal fluid (CSF) from histopathologically confirmed AD and control cases, using a new rapid immunoassay, the competitive enzyme-linked immunoflow assay (CELIFA), (ii) the determination of ubiquitin levels in brain tissue taken from the same cases, using a competitive enzyme-linked immunosorbent assay (ELISA), and (iii) an evaluation of the correlation between levels of ubiquitin in CSF and in brain tissue. Ubiquitin levels in CSF of AD and neurological control groups are significantly higher than those of non-neurological aged controls. Ubiquitin levels in brain homogenates of the AD group are significantly higher than those of both non-neurological aged and neurological control groups. The source of this increase in brain ubiquitin in AD is the particulate fraction, because ubiquitin levels in the brain cytosol fraction are the same among the three groups. In AD and non-neurological aged controls, there is a significant positive correlation between ubiquitin levels in CSF and in homogenate of cerebral white matter. In contrast, the correlation in the non-AD neurological control group has a negative tendency. These studies suggest that in AD, elevated levels of ubiquitin in the CSF reflect the increased amount of the protein in the brain and, therefore, can serve as a biomarker of the neuropathology in this disease.

Altered blood-brain-barrier function in Alzheimer's disease?

Alzheimer's disease (AD) and vascular dementia (VD) are the two most common causes of dementia. As yet, no definitive biological antemortem marker has been established for differential diagnosis of AD or VD. In this study, proteins of cerebrospinal fluid (CSF) from AD, VD and control patients were analyzed by two-dimensional (2-D) electrophoresis with immobilized pH gradients in the first dimension. No specific changes for AD or VD could be detected in the 2-D CSF patterns. However, a spot of haptoglobin alpha-1 chains (13.5 kDa; approximate pI 4.6) was found to be present in the majority of 2-D CSF maps from the dementia cases, suggesting a high-molecular-weight transudate type of alteration in the blood-brain barrier with considerable frequency in AD.

Concentration of neural thread protein in cerebrospinal fluid from progressive supranuclear palsy and Parkinson's disease

We measured the concentration of neural thread protein (NTP) in cerebrospinal fluid (CSF) by an automatized microparticle enzyme immunoassay from 11 progressive supranuclear palsy (PSP) patients and 11 Parkinson's disease (PD) patients and 7 patients with cervical spondylosis as controls. The mean levels did not differ significantly among the groups. In the PSP group, however, the levels correlated significantly with the severity of motor symptoms, signs and functional disability but not with dementia, while the opposite was true in the PD group. The elevated levels in PSP cases may reflect an increase with progression of the disease in such pathological structures as neurofibrillary tangles or neuropil threads, while in PD such levels may indicate associated Alzheimer-type pathology.

Neuronal thread protein over-expression in brains with Alzheimer's disease lesions

Neuronal thread protein (NTP) is a recently characterized molecule that is over-expressed in brains with Alzheimer's disease (AD) lesions. The present study encompasses a detailed analysis of NTP expression in AD compared with other neurodegenerative diseases and aged controls. Using a specific monoclonal antibody, NTP immunoreactivity was evaluated in 309 paraffin-embedded sections from 8 different regions of the frontal, parietal, and temporal lobes of 73 brains with AD, AD + Down's syndrome (DN), AD + Parkinson's disease (PD), PD dementia (PDD), aged controls, and disease controls with Huntington's disease, multi-infarct dementia, or schizophrenia. In 250 adjacent blocks of snap-frozen unfixed tissue the concentration of NTP (ng/mg of protein) was measured using a 3-site forward sandwich monoclonal antibody based immunoradiometric assay (M-IRMA). Immunohistochemical studies demonstrated that brains with AD, AD + PD, and AD + DN contained significantly higher densities of NTP immunoreactive neurons and more frequent immunostaining of neuropil and white matter fibers compared with PDD and aged controls (both P < 0.001) which had few or no AD lesions. In addition, the overall mean concentrations of NTP in AD, AD + PD, and AD + DN were significantly higher than in PDD and aged controls (P < 0.005). Greater degrees of NTP immunoreactivity and higher concentrations of the protein in cerebral tissue were significantly correlated with AD diagnosis and abundant neurofibrillary tangles (P < 0.005). The findings suggest that NTP over-expression may serve as a marker for the type of neuronal degeneration that occurs in AD.