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

The Association Between Plasma α-Synuclein (α-syn) Protein, Urinary Alzheimer-Associated Neuronal Thread Protein (AD7c-NTP), and Apolipoprotein Epsilon 4 (ApoE ε4) Alleles and Cognitive Decline in 60 Patients with Alzheimer's Disease Compared with 28 Age-Matched Normal Individuals

Background

Accumulating evidence has shown that α-synuclein (α-syn) pathology is involved in the pathophysiology of Alzheimer’s disease (AD). This study aimed to investigate the association between the levels of plasma α-syn protein, urinary Alzheimer-associated neuronal thread protein (AD7c-NTP), apolipoprotein epsilon 4 (ApoE ɛ4) alleles and cognitive decline in 60 AD patients compared with 28 age-matched normal controls (NCs) at a single center.

Material/Methods

All participants underwent α-syn, apolipoprotein E (ApoE), AD7c-NTP, cholesterol (CHO), high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triglycerides (TGs) analyses, neuropsychological scale assessments and neuroimaging analysis. Moreover, urine and peripheral blood samples were collected from all participants. The levels of plasma α-syn and AD7c-NTP were assayed using an enzyme-linked immunosorbent assay (ELISA) kit. Other test results were obtained from China-Japan Friendship Hospital.

Results

We found that plasma α-syn levels were significantly different between AD patients and NCs (p=0.045). α-Syn levels were also associated with AD7c-NTP (r=0.231, p=0.03) but not ApoE ɛ4 (Z=−0.147, p=0.883) levels. Neither α-syn [CHO (p=0.432), HDL (p=0.484), LDL (p=0.733) or TGs (p=0.253)] nor AD7c-NTP [CHO (p=0.867), HDL (p=0.13), LDL (p=0.57) or TGs (p=0.678)] had a relationship with lipids.

Conclusions

This study showed that the levels of plasma α-syn protein and urinary AD7c-NTP were significantly increased in AD patients compared with NCs, but not with ApoE alleles or serum lipid levels.

Reg-1α Promotes Differentiation of Cortical Progenitors via Its N-Terminal Active Domain

Reg-1α belongs to the Reg family of small, secreted proteins expressed in both pancreas and nervous system. Reg-1α is composed of two domains, an insoluble C-type lectin domain and a short soluble N-terminal peptide, which is released from the molecule upon proteolytic N-terminal processing, although the biological significance of this proteolysis remains unclear. We have previously shown that binding of Reg-1α to its receptor Extl3 stimulates axonal outgrowth. Reg-1α and Extl3 genes are expressed in the developing cortex but their expression decreases in adulthood, pointing to a possible function of this signaling system at the early developmental stages. Here, we demonstrate that recombinant Reg-1α increases migration and differentiation of cultured embryonic rat telencephalic progenitors via the activation of GSK-3β activity. In vivo overexpression of Reg-1α by in utero electroporation, has a similar effect, favoring premature differentiation of cortical progenitors. Notably, the N-terminal soluble domain, but not the C-type lectin domain, is largely responsible for Reg-1α effects on cortical neuronal differentiation. We thus conclude that Reg-1α via its proteolytically generated N-terminal domain is required for basic development processes.

The relationship between urinary Alzheimer-associated neuronal thread protein and blood biochemical indicators in the general population

Urinary Alzheimer-associated neuronal thread protein (AD7c-NTP) is elevated in early Alzheimer's disease (AD) and mild cognitive impairment, and is considered a biomarker for the early diagnosis of AD. However, it has not yet been investigated whether urinary AD7c-NTP is elevated with increases in blood biochemical indicators related to AD risk factors. We recruited 2180 participants, aged 35-93 years, from communities of four districts in Beijing. Blood biochemical indicators, including blood glucose, blood lipids, renal function, and high-sensitivity C-reactive protein, were measured using routine methods. Urinary AD7c-NTP was detected using an enzyme-linked immunosorbent assay AD7c-NTP kit. In the general population, there were no significant differences in urinary AD7c-NTP levels in subjects with different Mini-Mental State Examination levels or C-reactive protein values. After adjusting for age and sex, there were significant differences in urinary AD7c-NTP levels between different education levels, marital statuses, blood glucose, blood lipids, and kidney function. There was a negative correlation between urinary AD7c-NTP levels and serum creatinine (r = -0.128). There was a positive correlation between urinary AD7c-NTP levels and HbA1c (r = 0.104), insulin (r = 0.101), and triglycerides (r = 0.093). Urinary AD7c-NTP might be useful as a potential indicator to predict AD risk.

Regenerating islet-derived 1α (Reg-1α) protein is new neuronal secreted factor that stimulates neurite outgrowth via exostosin Tumor-like 3 (EXTL3) receptor

Regenerating islet-derived 1α (Reg-1α)/lithostathine, a member of a family of secreted proteins containing a C-type lectin domain, is expressed in various organs and plays a role in proliferation, differentiation, inflammation, and carcinogenesis of cells of the digestive system. We previously reported that Reg-1α is overexpressed during the very early stages of Alzheimer disease, and Reg-1α deposits were detected in the brain of patients with Alzheimer disease. However, the physiological function of Reg-1α in neural cells remains unknown. Here, we show that Reg-1α is expressed in neuronal cell lines (PC12 and Neuro-2a) and in rat primary hippocampal neurons (E17.5). Reg-1α is mainly localized around the nucleus and at the membrane of cell bodies and neurites. Transient overexpression of Reg-1α or addition of recombinant Reg-1α significantly increases the number of cells with longer neurites by stimulating neurite outgrowth. These effects are abolished upon down-regulation of Reg-1α by siRNA and following inhibition of secreted Reg-1α by antibodies. Moreover, Reg-1α colocalizes with exostosin tumor-like 3 (EXTL3), its putative receptor, at the membrane of these cells. Overexpression of EXTL3 increases the effect of recombinant Reg-1α on neurite outgrowth, and Reg-1α is not effective when EXTL3 overexpression is down-regulated by shRNA. Our findings indicate that Reg-1α regulates neurite outgrowth and suggest that this effect is mediated by its receptor EXTL3.

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.

Competitive ELISA studies of neural thread protein in urine in Alzheimer's disease

A specific and reliable competitive affinity assay kit has been developed to quantitatively measure neural thread protein (NTP) in first morning urine samples. This assay, called the urine neural thread protein test (UNTP), is a competitive enzyme-linked immunosorbent assay (ELISA) format affinity assay using 32-well microtiter plates. The assay detects UNTP in the 10-60 microg/mL range (an improvement over earlier assays of 10(3) x ), is linear and more reproducible (average coefficient of variation [CV] 6.2% in precision studies). The utility of the assay has been demonstrated in urine samples from patients with Alzheimer's disease (AD) and controls (sensitivity of 90% and specificity of 91%). Test-retest assays of subjects with AD and controls were comparatively stable at intervals of 2 days to 4.5 years, which suggests that positive (elevated) or negative (normal) NTP levels do not fluctuate significantly over time with respect to the cutoff.

A Sick Eye in a Sick Body? Systemic Findings in Patients with Primary Open-angle Glaucoma

Despite intense research, the pathogenesis of primary open-angle glaucoma (POAG) is still not completely understood. There is ample evidence for a pathophysiological role of elevated intraocular pressure; however, several systemic factors may influence onset and progression of the disease. Systemic peculiarities found in POAG include alterations of the cardiovascular system, autonomic nervous system, immune system, as well as endocrinological, psychological, and sleep disturbances. An association between POAG and other neurodegenerative diseases, such as Alzheimer disease and Parkinson disease, has also been described. Furthermore, the diagnosis of glaucoma can affect the patient's quality of life. By highlighting the systemic alterations found in POAG, this review attempts to bring glaucoma into a broader medical context.

Role and distribution of retinoic acid during CNS development

Retinoic acid (RA), the biologically active derivative of vitamin A, induces a variety of embryonal carcinoma and neuroblastoma cell lines to differentiate into neurons. The molecular events underlying this process are reviewed with a view to determining whether these data can lead to a better understanding of the normal process of neuronal differentiation during development. Several transcription factors, intracellular signaling molecules, cytoplasmic proteins, and extracellular molecules are shown to be necessary and sufficient for RA-induced differentiation. The evidence that RA is an endogenous component of the developing central nervous system (CNS) is then reviewed, data which include high-pressure liquid chromotography (HPLC) measurements, reporter systems and the distribution of the enzymes that synthesize RA. The latter is particularly relevant to whether RA signals in a paracrine fashion on adjacent tissues or whether it acts in an autocrine manner on cells that synthesize it. It seems that a paracrine system may operate to begin early patterning events within the developing CNS from adjacent somites and later within the CNS itself to induce subsets of neurons. The distribution of retinoid-binding proteins, retinoid receptors, and RA-synthesizing enzymes is described as well as the effects of knockouts of these genes. Finally, the effects of a deficiency and an excess of RA on the developing CNS are described from the point of view of patterning the CNS, where it seems that the hindbrain is the most susceptible part of the CNS to altered levels of RA or RA receptors and also from the point of view of neuronal differentiation where, as in the case of embryonal carcinoma (EC) cells, RA promotes neuronal differentiation. The crucial roles played by certain genes, particularly the Hox genes in RA-induced patterning processes, are also emphasized.

Alzheimer's disease as a disorder of mechanisms underlying structural brain self-organization

Mental function has as its cerebral basis a specific dynamic structure. In particular, cortical and limbic areas involved in "higher brain functions" such as learning, memory, perception, self-awareness and consciousness continuously need to be self-adjusted even after development is completed. By this lifelong self-optimization process, the cognitive, behavioural and emotional reactivity of an individual is stepwise remodelled to meet the environmental demands. While the presence of rigid synaptic connections ensures the stability of the principal characteristics of function, the variable configuration of the flexible synaptic connections determines the unique, non-repeatable character of an experienced mental act. With the increasing need during evolution to organize brain structures of increasing complexity, this process of selective dynamic stabilization and destabilization of synaptic connections becomes more and more important. These mechanisms of structural stabilization and labilization underlying a lifelong synaptic remodelling according to experience, are accompanied, however, by increasing inherent possibilities of failure and may, thus, not only allow for the evolutionary acquisition of "higher brain function" but at the same time provide the basis for a variety of neuropsychiatric disorders. It is the objective of the present paper to outline the hypothesis that it might be the disturbance of structural brain self-organization which, based on both genetic and epigenetic information, constantly "creates" and "re-creates" the brain throughout life, that is the defect that underlies Alzheimer's disease (AD). This hypothesis is, in particular, based on the following lines of evidence. (1) AD is a synaptic disorder. (2) AD is associated with aberrant sprouting at both the presynaptic (axonal) and postsynaptic (dendritic) site. (3) The spatial and temporal distribution of AD pathology follows the pattern of structural neuroplasticity in adulthood, which is a developmental pattern. (4) AD pathology preferentially involves molecules critical for the regulation of modifications of synaptic connections, i.e. "morphoregulatory" molecules that are developmentally controlled, such as growth-inducing and growth-associated molecules, synaptic molecules, adhesion molecules, molecules involved in membrane turnover, cytoskeletal proteins, etc. (5) Life events that place an additional burden on the plastic capacity of the brain or that require a particularly high plastic capacity of the brain might trigger the onset of the disease or might stimulate a more rapid progression of the disease. In other words, they might increase the risk for AD in the sense that they determine when, not whether, one gets AD. (6) AD is associated with a reactivation of developmental programmes that are incompatible with a differentiated cellular background and, therefore, lead to neuronal death. From this hypothesis, it can be predicted that a therapeutic intervention into these pathogenetic mechanisms is a particular challenge as it potentially interferes with those mechanisms that at the same time provide the basis for "higher brain function".

Altered gene expression in lymphocytes of patients with normal-tension glaucoma

BACKGROUND

In glaucoma there is a loss of retinal ganglion cells. There is evidence that this loss can occur by apoptosis. The signal transduction leading to retinal ganglion cell apoptosis in glaucoma is not yet clear. The present study compares the gene expression in lymphocytes of normal tension glaucoma patients (NTG-patients) with the one of healthy controls.

METHODS

Subtractive hybridization was used to compare mRNA in lymphocytes of six vasospastic NTG-patients with six age and sex matched healthy subjects.

RESULTS

Genes coding for p53-protein, NTP (neural thread protein) and 20 S proteasome subunit XAPC7 were overexpressed, whereas those coding for XPGC (Xeroderma pigmentosum gene), the survivin protein as well as one type of ABC transport protein were underexpressed.

CONCLUSION

In comparison to healthy controls, patients with vasospastic NTG seem to over- as well as under-express certain genes in their lymphocytes.

Molecular abnormalities of the brain in Down syndrome: relevance to Alzheimer's neurodegeneration

Down syndrome is caused by over-expression of genes located within a segment of chromosome 21, termed the Down locus. Down syndrome is associated with developmental abnormalities of the central nervous system that result in mental retardation and age-dependent Alzheimer-type neurodegeneration. Some of the neurodegenerative lesions, including A beta amyloid deposition, apoptotic cell death, and aberrant dendritic arborization, are in part due to constitutively increased expression of genes that encode the amyloid precursor protein, superoxide dismutase I, and S100-beta, and located within the Down locus. However, neurodegeneration in Down syndrome is also associated with aberrant expression of genes that are not linked to the Down locus, including the growth associated protein, GAP-43, nitric oxide synthase 3, neuronal thread protein, and pro-apoptosis genes such as p53, Bax, and interleukin-1 beta-converting enzyme. Increased expression of these non-Down locus genes correlates with proliferation of dystrophic neurites and apoptotic cell death, two important correlates of cognitive impairment in Alzheimer's disease. This article reviews the functional importance of abnormal gene expression in relation to Alzheimer-type neurodegeneration in brains of individuals with Down syndrome.

Heat-shock protein 70 levels in brain of patients with Down syndrome and Alzheimer's disease

Heat-shock proteins are proteins serving as molecular chaperones, involved in the protection of cells from various forms of stress. Since the expression of these proteins is closely related to that of amyloid precursor protein (APP), heat-shock protein has been studied in brain of patients with Alzheimer's disease (AD) and furthermore, brain Hsp70 mRNA levels were related to the agonal state. The aim of our study was to demonstrate the presence of Hsp70--immunoreactive protein in brain of controls, patients with AD and Down Syndrome (DS) in individual brain regions. The rationale for the study was to test the hypothesis that expression of Hsp70, a protein involved in apoptosis would be altered in brain of these patients with neurodegenerative disorders where (neuronal) apoptosis is a hallmark of the disease. Brain immunoreactive-Hsp70--protein (Hsp70) was determined by Western blotting using specific monoclonal antibody in five different brain regions (frontal, parietal, occipital, temporal cortex and cerebellum) from controls, DS and AD patients. Hsp70 expression was significantly increased in temporal cortex of patients with AD (arbitrary units: means +/- SD; 0.35 +/- 0.49 for controls, 0.97 +/- 0.70 for DS patients, 1.16 +/- 0.56 for AD patients). In frontal and parietal cortex from DS patients, there was a strong correlation between Hsp70 levels and the length of post-mortem interval (r = 0.95, P < 0.01 and r = 0.82, P < 0.021).

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.