Quantification of plasma phosphorylated tau to use as a biomarker for brain Alzheimer pathology: pilot case-control studies including patients with Alzheimer's disease and down syndrome.

BACKGROUND: There is still a substantial unmet need for less invasive and lower-cost blood-based biomarkers to detect brain Alzheimer's disease (AD) pathology. This study is aimed to determine whether quantification of plasma tau phosphorylated at threonine 181 (p-tau181) is informative in the diagnosis of AD. METHODS: We have developed a novel ultrasensitive immunoassay to quantify plasma p-tau181, and measured the levels of plasma p-tau181 in three cohorts. RESULTS: In the first cohort composed of 20 AD patients and 15 age-matched controls, the plasma levels of p-tau181 were significantly higher in the AD patients than those in the controls (0.171 ± 0.166 pg/ml in AD versus 0.0405 ± 0.0756 pg/ml in controls, p = 0.0039). The percentage of the subjects whose levels of plasma p-tau181 exceeded the cut-off value (0.0921 pg/ml) was significantly higher in the AD group compared with the control group (60% in AD versus 16.7% in controls, p = 0.0090). In the second cohort composed of 20 patients with Down syndrome (DS) and 22 age-matched controls, the plasma concentrations of p-tau181 were significantly higher in the DS group (0.767 ± 1.26 pg/ml in DS versus 0.0415 ± 0.0710 pg/ml in controls, p = 0.0313). There was a significant correlation between the plasma levels of p-tau181 and age in the DS group (R2 = 0.4451, p = 0.0013). All of the DS individuals showing an extremely high concentration of plasma p-tau181 (> 1.0 pg/ml) were older than the age of 40. In the third cohort composed of 8 AD patients and 3 patients with other neurological diseases, the levels of plasma p-tau181 significantly correlated with those of CSF p-tau181 (R2 = 0.4525, p = 0.023). CONCLUSIONS: We report for the first time quantitative data on the plasma levels of p-tau181 in controls and patients with AD and DS, and these data suggest that the plasma p-tau181 is a promising blood biomarker for brain AD pathology. This exploratory pilot study warrants further large-scale and well-controlled studies to validate the usefulness of plasma p-tau181 as an urgently needed surrogate marker for the diagnosis and disease progression of AD.

Hypoxia induces expression of a GPI-anchorless splice variant of the prion protein.

The human prion protein (PrP) is a glycoprotein with a glycosylphosphatidylinositol (GPI) anchor at its C-terminus. Here we report alternative splicing within exon 2 of the PrP gene (PRNP) in the human glioblastoma cell line T98G. The open reading frame of the alternatively spliced mRNA lacked the GPI anchor signal sequence and encoded a 230 amino acid polypeptide. Its product, GPI-anchorless PrP (GPI(-) PrPSV), was unglycosylated and soluble in non-ionic detergent, and was found in the cytosolic fraction. We also detected low levels of alternatively spliced mRNA in human brain and non-neuronal tissues. When long-term passaged T98G cells were placed in a low-oxygen environment, alternatively spliced mRNA expression increased and expression of normally spliced PrP mRNA decreased. These findings imply that oxygen tension regulates GPI(-) PrPSV expression in T98G cells.

Sterol regulatory element-binding protein-2- and liver X receptor-driven dual promoter regulation of hepatic ABC transporter A1 gene expression: mechanism underlying the unique response to cellular cholesterol status.

ABC transporter A1 (ABCA1) mediates and rate-limits biogenesis of high density lipoprotein (HDL), and hepatic ABCA1 plays a major role in regulating plasma HDL levels. HDL generation is also responsible for release of cellular cholesterol. In peripheral cells ABCA1 is up-regulated by the liver X receptor (LXR) system when cell cholesterol increases. However, cholesterol feeding has failed to show a significant increase in hepatic ABCA1 gene expression, and its expression is up-regulated by statins (3-hydroy-3-methylglutaryl-CoA reductase inhibitors), suggesting distinct regulation. In this study we investigated the mechanism of regulation of the rat hepatic ABCA1 gene and identified two major ABCA1 transcripts and two corresponding promoter regions. Compactin activated the novel liver-type promoter in rat hepatoma McARH7777 cells by binding the sterol regulatory element-binding protein-2 (SREBP-2). In contrast, compactin repressed the previously identified peripheral-type promoter in an LXR-responsive element-dependent but not E-box-dependent manner. Thus, compactin increased the liver-type transcript and decreased the peripheral-type transcript. The same two transcripts were also dominant in human and mouse livers, whereas the intestine contains only the peripheral-type transcript. Treatment of rats with pravastatin and a bile acid binding resin (colestimide), which is known to activate SREBP-2 in the liver, caused a reduction in the hepatic cholesterol level and the same differential responses in vivo, leading to increases in hepatic ABCA1 mRNA and protein and plasma HDL levels. We conclude that the dual promoter system driven by SREBP-2 and LXR regulates hepatic ABCA1 expression and may mediate the unique response of hepatic ABCA1 gene expression to cellular cholesterol status.

Propagation of a protease-resistant form of prion protein in long-term cultured human glioblastoma cell line T98G.

Human prion diseases, such as Creutzfeldt-Jakob disease (CJD), a lethal, neurodegenerative condition, occur in sporadic, genetic and transmitted forms. CJD is associated with the conversion of normal cellular prion protein (PrP(C)) into a protease-resistant isoform (PrP(res)). The mechanism of the conversion has not been studied in human cell cultures, due to the lack of a model system. In this study, such a system has been developed by culturing cell lines. Human glioblastoma cell line T98G had no coding-region mutations of the prion protein gene, which was of the 129 M/V genotype, and expressed endogenous PrP(C) constitutively. T98G cells produced a form of proteinase K (PK)-resistant prion protein fragment following long-term culture and high passage number; its deglycosylated form was approximately 18 kDa. The PK-treated PrP(res) was detected by immunoblotting with the mAb 6H4, which recognizes residues 144-152, and a polyclonal anti-C-terminal antibody, but not by the mAb 3F4, which recognizes residues 109-112, or the anti-N-terminal mAb HUC2-13. These results suggest that PrP(C) was converted into a proteinase-resistant form of PrP(res) in T98G cells.

Alpha-melanocyte-stimulating hormone stimulates prolactin secretion through melanocortin-3 receptors expressed in mammotropes in the mouse pituitary.

The intermediate lobe of rodent pituitaries is involved in the regulation of prolactin (PRL) secretion from the anterior lobe. In a previous study, we demonstrated the stimulatory effect of alpha-melanocyte-stimulating hormone (alpha-MSH) on PRL release and the expression of melanocortin-3 receptors (MC3-Rs) in cultured mouse pituitary cells. The aim of the present study was to clarify whether alpha-MSH directly stimulates PRL release through the MC3-Rs by determining the cell type of MC3-R-expressing cells in the mouse pituitary anterior lobe. Northern blot analysis revealed a 2.7-kb transcript for MC3-R mRNA in the anterior and neurointermediate lobes of pituitary glands of adult male and female mice. Dual cellular localization of MC3-R mRNA and PRL or growth hormone (GH) in the mouse pituitary glands was performed by in situ hybridization analysis of MC3-R mRNA followed by immunocytochemical detection of PRL or GH. MC3-R mRNA was detected in most mammotropes and some somatotropes. alpha-MSH increased PRL release and stimulated DNA replication in mammotropes, and these effects were blocked by SHU9119, an antagonist of MC3-R and MC4-R. These results indicate that alpha-MSH stimulates PRL release and proliferation of mammotropes through MC3-Rs, and suggest that alpha-MSH from intermediate lobes can regulate mammotrope functions in the mouse pituitary.

Gene expression and the physiological role of transforming growth factor-alpha in the mouse pituitary.

Transforming growth factor-alpha (TGF-alpha), a member of the epidermal growth factor (EGF) family, is produced within the mouse anterior pituitaries. However, the cell types of TGF-alpha-expressing cells and the physiological roles of TGF-alpha within mouse pituitary glands remain unclear. The aim of the present study was to localize TGF-alpha mRNA-expressing cells, and to clarify the involvement of TGF-alpha in estrogen-induced DNA replication in mouse anterior pituitary cells. Northern blot analysis demonstrated TGF-alpha mRNA expression in adult male and female mouse anterior pituitaries. In situ hybridization analysis of the pituitaries in these mice showed that TGF-alpha mRNA-expressing cells in the anterior pituitary are round, oval, and medium-sized. TGF-alpha mRNA was colocalized in most of the growth hormone (GH) mRNA-expressing cells, while only some of the prolactin (PRL) mRNA-expressing cells. DNA replication in the anterior pituitary cells was detected by monitoring the cellular uptake of a thymidine analogue, bromodeoxyuridine (BrdU) in a primary serum-free culture system. Estradiol-17beta (E2) and TGF-alpha treatment increased the number of BrdU-labelled mammotrophs, indicating that E2 and TGF-alpha treatment stimulates the DNA replication in mammotrophs. Immunoneutralization of TGF-alpha with anti-TGF-alpha-antibodies nullified the E2-induced increase in DNA replication. RT-PCR analysis of TGF-alpha mRNA expression in ovariectomized female mice revealed that E2 increases TGF-alpha mRNA levels. These results indicate that the TGF-alpha produced primarily in the somatotrophs mediates the stimulatory effects of estrogen on the DNA replication of pituitary cells in a paracrine or autocrine manner.

[Study on the detection of prion protein in food products by a competitive enzyme-linked immunosorbent assay].

We developed a competitive enzyme-linked immunosorbent assay (ELISA) to detect prion protein contained in materials derived from cattle, aiming at establishing a method to detect abnormal prion protein (PrPSc) in food products. Rabbit polyclonal antibodies were raised against bovine prion peptides. Using these antibodies, we have established a competitive ELISA that is capable of detecting recombinant bovine prion protein (rBoPrP) in the range of 12 to 1,200 ng and we used it to determine prion protein contents in bovine cerebral cortex. This assay system was evaluated by spiking food products with various amounts of rBoPrP. The determination gave 2-fold higher values in minced meat homogenates and lower values in large intestine homogenates than the values expected from the spiked amounts. This assay provides a simple determination method of spiked rBoPrP, and therefore is expected to be useful for investigating sample pretreatment methods.

Induction of mammotroph development by a combination of epidermal growth factor, insulin, and estradiol-17beta in rat pituitary tumor GH3 cells.

Several reports have indicated that prolactin-secreting cells (PRL cells) are generated from growth hormone-secreting cells (GH cells). We have shown that treatment with a combination of epidermal growth factor (EGF), insulin, and estradiol-17beta (E (2)) induces the appearance of PRL cells in pituitary tumor GH3 cells. The aim of the present study was to clarify the involvement of mitosis in the cytogenesis of PRL cells in rat pituitary and GH3 cells. The effects of the treatment with EGF, insulin and E(2) on DNA-replication were studied by detecting the uptake of bromodeoxyuridine (BrdU) into the nucleus. In cultured rat pituitary cells, BrdU-labeled PRL cells were observed irrespective of the hormone treatment. In GH3 cells, BrdU-labeled GH cells and mammosomatotrophs (MS cells) were detected; BrdU-labeled PRL cells were not detected, however, when GH3 cells were treated with BrdU for 3 hr and then immediately examined for BrdU-labeling. BrdU-labeled PRL cells were found only when GH3 cells treated with BrdU were allowed to grow for another 3 days. This finding suggests that during the additional 3-day culture, BrdU-labeled PRL cells were generated from BrdU-labeled cells other than PRL cells. These results indicate that PRL cells are transdifferentiated from GH cells or MS cells in GH3 cells by a combined treatment with EGF, insulin and E(2), while PRL cells in rat pituitaries are able to proliferate in response to the hormone treatment. Thus, there may be two pathways for cytogenesis of PRL cells: the transdifferentiation of GH cells or MS cells, and a self-duplication of PRL cells.

G1-dependent prion protein expression in human glioblastoma cell line T98G.

Human glioblastoma cell line T98G produced a cellular form of prion protein (PrP(C)), and we confirmed expression of PrP mRNA by RT-PCR. Immunoblot analysis of whole cell lysate revealed one major (35 kDa) and two faint bands (31, 25 kDa) that reacted with monoclonal anti-human PrP antibody 3F4. Cells treated with tunicamycin produced only a 25 kDa band, representing a deglycosylated form of PrP. Similarly, peptide: N-glycosidase F treatment of whole cell lysate altered the Asn-linked form to the deglycosylated form. When T98G cells were cultured for a longer period, the amount of PrP(C) per cell increased on Day 4 to 16 in a time-dependent manner. When the cells were cultured at high cell-density, the cells on Day 4 produced the same amount of PrP(C) as those on Day 16 of the usual culture. Moreover, in a serum-free medium, cells cultured at a low cell-density produced the same amount of PrP(C) as those cultured at the high cell-density. These results demonstrate that PrP(C) production in T98G cells was dependent on the phase of the cell cycle, probably the G1 phase.