Simplified RT/PCR quantitation of gene transcripts in cultured neuroblastoma (SN49) and microglial (BV-2) cells using capillary electrophoresis and laser-induced fluorescence

Identification of nine alternatively spliced alpha2,3-sialyltransferase, ST3Gal IV, transcripts and analysis of their expression by RT-PCR and laser-induced fluorescent capillary electrophoresis (LIF-CE) in twenty-one human tissues

In order to characterise the candidate alpha2,3-sialyltransferases necessary for biosynthesis of the selectin ligand SLe(x) and related antigens we have cloned and sequenced, from peripheral blood leukocytes of single individuals, various transcripts from the human ST3Gal III, IV and VI genes. Our clones have revealed a considerable heterogeneity in transcript isoforms. Among our ST3Gal IV clones we isolated nine alternatively spliced transcripts covering the coding region of the human ST3Gal IV gene (A1, A1 - 12, A1 + 18, A2, A2 - 12, A2 + 18, B, B - 12 and B + 18). Five of these isotranscripts A1 - 12, A1 + 18, A2 - 12, A2 + 18 and B + 18 have not been described before. In order to investigate if the alternatively spliced isotranscripts were specific for human PBL, we analysed the expression by RT-PCR and laser-induced fluorescent capillary electrophoresis (LIF-CE) in twenty other human tissues. We found a tissue specific expression of ST3Gal IV A1, A1 - 12, A1 + 18, A2, A2 - 12, A2 + 18 and B + 18 as well as a general expression of ST3Gal IV B and B - 12 isotranscripts in all tissues examined.

In-situ sampling and separation of RNA from individual mammalian cells

In this investigation RNA was directly sampled and separated at the single-cell level (without extraction) by capillary electrophoresis (CE). Laser-induced fluorescence (LIF) was employed to detect ethidium bromide-labeled RNA molecules under native conditions. Hydroxypropylmethylcellulose was used as a matrix for molecular sieving. Additives to the polymer solution included poly(vinylpyrrolidone) to eliminate the electroosmotic flow and mannitol to enhance the separation. Peak identities were confirmed as RNA by enzymatic treatment with RNase I. The individual Chinese Hamster Ovary (CHO-K1) cells were injected into a capillary and the cells were lysed online with sodium dodecyl sulfate (SDS) solutions before running electrophoresis. Low molecular mass (LMM) RNAs as well as larger fragments (tentatively identified as 18S and 28S ribosomal RNA by comparison with the literature) were detected with this system, which corresponds to a detected amount of approximately equals 10-20 pg of RNA/cell. A Proteinase K study showed that proteins incorporated with RNA molecules were eliminated by SDS treatment and thus did not influence the migration of RNA. Experiments were also performed with this technique to detect nucleic acid damage. Changes in the peak pattern were detected in the cells treated with hydrogen peroxide, which meant that strand breaks occurred in DNA and RNA. It was found that 60 mM caused the most severe damage to the nucleic acids.

Quantification of relative mRNA expression in the rat brain using simple RT-PCR and ethidium bromide staining

We developed a protocol for quantification of relative gene expression using reverse transcription-polymerase chain reaction (RT-PCR) without the use of radioisotopes, special equipment or extra nucleotide fragments, such as competitors. The relative gene expression of GABA(A) receptor beta(1) subunit (GABA(A)Rbeta(1)) and phospholipase C beta(4) subtype (PLCbeta(4)) in rat cerebrum and cerebellum were determined by comparing the ratio of PCR products generated by linear amplification of the target cDNA segments and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) cDNA segment as a reference. The density of PCR products was measured from digitized images of photographs of ethidium-bromide-stained agarose gels. The linear region of PCR amplification was within the linear range (from 0.3 to 12 ng DNA in a single band) of the detection system. The accuracy of the present method was <2-fold difference in gene expression in a single determination and a 1.5-fold difference was statistically significant after repeated measurements. The estimated relative expression of PLCbeta(4) was significantly higher in cerebellum than cerebrum, and that of GABA(A)Rbeta(1) was the same in these two regions. Using the present method, it is possible to quantify several different subunits and subtypes of known ion channel, neurotransmitter receptor and intracellular signaling enzyme gene families.

Retinoic acid-mediated enhancement of the cholinergic/neuronal nitric oxide synthase phenotype of the medial septal SN56 clone: establishment of a nitric oxide-sensitive proapoptotic state

It is unclear what mechanisms lead to the degeneration of basal forebrain cholinergic neurons in Alzheimer's or other human brain diseases. Some brain cholinergic neurons express neuronal nitric oxide (NO) synthase (nNOS), which produces a free radical that has been implicated in some forms of neurodegeneration. We investigated nNOS expression and NO toxicity in SN56 cells, a clonal cholinergic model derived from the medial septum of the mouse basal forebrain. We show here that, in addition to expressing choline acetyltransferase (ChAT), SN56 cells express nNOS. Treatment of SN56 cells with retinoic acid (RA; 1 microM) for 48 h increased ChAT mRNA (+126%), protein (+88%), and activity (+215%) and increased nNOS mRNA (+98%), protein (+400%), and activity (+15%). After RA treatment, SN56 cells became vulnerable to NO excess generated with S-nitro-N-acetyl-DL-penicillamine (SNAP) and exhibited increased nuclear DNA fragmentation that was blocked with a caspase-3 inhibitor. Treatment with dexamethasone, which largely blocked the RA-mediated increase in nNOS expression, or inhibition of nNOS activity with methylthiocitrulline strongly potentiated the apoptotic response to SNAP in RA-treated SN56 cells. Caspase-3 activity was reduced when SNAP was incubated with cells or cell lysates, suggesting that NO can directly inhibit the protease. Thus, whereas RA treatment converts SN56 cells to a proapoptotic state sensitive to NO excess, endogenously produced NO appears to be anti-apoptotic, possibly by tonically inhibiting caspase-3.

New anti-inflammatory treatment strategy in Alzheimer's disease

Numerous reports have indicated that patients suffering from inflammatory diseases (e.g., arthritis) who take anti-inflammatory medication have a reduced risk of developing Alzheimer's disease (AD). Thus, the first generation of anti-inflammatory cyclooxygenase (COX) inhibitors, such as aspirin and indomethacin, have been tested as potential therapeutics in AD. Because the inhibition of COX-1 is also known to cause tissue damage in the gastrointestinal system from the resultant reduced cytoprotection, selective COX-2 inhibitors are being investigated and tested clinically as potentially better therapeutics for AD patients. However, such drugs may also trigger unwanted effects; for example, the COX-2 inhibitors, which reduce the production of one type of eicosanoids, the prostaglandins, may increase the production of other eicosanoids; i.e., the leukotriene B4 (LTB4), which is one of the most potent endogenous chemotactic/inflammatory factors. LTB4 production is initiated by the enzyme 5-lipoxygenase (5-LOX). The expression of the 5-LOX gene is upregulated during neurodegeneration and with aging. In spite of the fact that 5-LOX and leukotrienes are major players in the inflammation cascade, their role in AD pathobiology/therapy has not been extensively investigated. We propose that the 5-LOX inflammatory cascade may take part in the process of aging-associated neurodegenerative diseases, and we point to the role of 5-LOX in neurodegeneration and discuss its relevance for anti-inflammatory therapy of AD.

Macrophage colony-stimulating factor augments beta-amyloid-induced interleukin-1, interleukin-6, and nitric oxide production by microglial cells

In Alzheimer's disease (AD), a chronic cerebral inflammatory state is thought to lead to neuronal injury. Microglia, intrinsic cerebral immune effector cells, are likely to be key in the pathophysiology of this inflammatory state. We showed that macrophage colony-stimulating factor, a microglial activator found at increased levels in the central nervous system in AD, dramatically augments beta-amyloid peptide (betaAP)-induced microglial production of interleukin-1, interleukin-6, and nitric oxide. In contrast, granulocyte macrophage colony-stimulating factor, another hematopoietic cytokine found in the AD brain, did not augment betaAP-induced microglial secretory activity. These results indicate that increased macrophage colony-stimulating factor levels in AD could magnify betaAP-induced microglial inflammatory cytokine and nitric oxide production, which in turn could intensify the cerebral inflammatory state by activating astrocytes and additional microglia, as well as directly injuring neurons.

Indicators of glial activation and brain oxidative stress after intraventricular infusion of endotoxin

Glial activation and oxidative stress are both consequences of brain aging. To investigate whether glial activation causes oxidative stress or not, the immune activator, lipopolysaccharide (LPS), was intraventricularly injected into the rat brain. The expression of candidate genes were examined by in situ hybridization histochemistry (ISHH) combined with immunohistochemistry for glial markers over a period of time up to 24 h after the LPS injection. The mRNA for glial fibrillary acidic protein (GFAP) was elevated around the injection site by 2 h, and the volume of elevated expression spread to the entire brain after 6 h, with higher levels present in the injected hemisphere. The level of inducible isoform of nitric oxide synthase (i-NOS) mRNA increased in a punctate-like pattern in the region of the injection by 6 h and this response spread to the entire brain after 12 h. These results indicate that the glia are activated for at least 24 h after a single LPS injection. The mRNAs for a heat-shock protein (HSP70) and for the manganese-dependent superoxide dismutase (Mn-SOD) were elevated in the ipsilateral hemisphere as early as 2 h post-injection, but these responses subsided nearly to basal levels by 4 h. These levels of mRNAs for these genes increased again after 6 h of the LPS injection; thus, the earlier increases of the messages appeared to be associated with the survival surgery procedure. With microautoradiographic analysis, scattered OX-42 positive cells expressed i-NOS mRNA after 6 h post-injection, but elevation of Mn-SOD mRNA was not detected in either microglia or astrocytes at any time point examined. The level for Cu/Zn-SOD mRNA did not alter at any time point. The beta-amyloid precursor protein (betaAPP) mRNAs were elevated beginning at 6 h. These results indicate that chronic glial activation leads to a condition of oxidative stress in the brain. The data also suggest that LPS injection could be used to study the effects of chronic glial activation on the survival of neuronal populations that could be at risk from oxidative stress.

Septo-hippocampal cholinergic and neurotrophin markers in age-induced cognitive decline

Messenger RNA (mRNA) molecules encoding proteins related to the presynaptic cholinergic and neurotrophin systems were quantitated in the hippocampus and basal forebrain of Long-Evans rats with spatial learning ability assessed in the Morris water maze. The reverse transcriptase-polymerase chain reaction showed that the mRNAs for the low-affinity neurotrophin receptor (p75-NTR) and the growth-associated protein GAP-43 were decreased in level in the basal forebrain of aged-impaired rats. In the hippocampus of these aged-impaired rats, the mRNA for VGF, another neurotrophin-inducible gene, also was decreased. In situ hybridization histochemistry revealed that mRNAs for nerve growth factor (NGF) and brain-derived neurotrophic factor increased in level in the aged rat hippocampus; when age effects were removed, NGF mRNA level remained significantly correlated with maze performance. Enzyme-linked immunosorbent assay indicated that NGF protein was expressed at normal levels in the aged rat hippocampus. These mRNA and protein alterations may signify that a defect in neurotrophin signaling exists in the brains of aged Long-Evans rats, underlying reduced plasticity responses in the basal forebrain cholinergic system.

Use of capillary electrophoresis with laser-induced fluorescence detection to assess messenger ribonucleic acid molecules amplified by the polymerase chain reaction: applications in the cloning of cells

Progressive and selective degeneration of specific classes of neurons occurs in the Alzheimer's disease (AD) brain. Differential vulnerability in this disease is evident even within supopulations that synthesize and release acetylcholine as a transmitter; i.e., basal forebrain cholinergic neurons degenerate but other classes of cholinergic neurons are relatively preserved. The basis for this selective vulnerability is unknown. Studies of differential neuronal vulnerability in AD would be facilitated if cell lines expressing neurotransmitter-specific phenotypes could be cloned from the brain. Capillary electrophoresis (CE) with laser-induced fluorescence (LIF) has been shown to be a sensitive method of detection and quantitation of the DNA products of the polymerase chain reaction (PCR). CE/LIF was combined with the PCR to detect phenotypic messenger RNA (mRNA) molecules, converted to cDNA using reverse transcriptase (RT), in cultures of virally immortalized brainstem progenitor cells produced during establishment of a cloning strategy. RT/PCR methods were developed for detection of the mRNAs for choline acetyltransferase (ChAT), the neuronal, constitutive isoform of nitric oxide synthase (c-NOS), and the growth-associated protein GAP-43, three genes known to be expressed in central cholinergic neurons. A "nondestructive" method of screening cultured cells for their expression of c-NOS was established using depolarization with medium containing 50 mM potassium ion. These approaches were first validated using cultured SN56 (cholinergic) and N1E-115 (c-NOS-positive) neuroblastoma cells, and with primary brainstem cultures. For the cloning of novel cell lines, progenitor cells were isolated from the embryonic day 13 fetal brainstem and were immortalized by transfection with a retroviral vector that confers a temperature-sensitive SV-40 transforming activity and neomycin resistance. Cell colonies surviving in G418-containing media were isolated and cloned by dilution. Clonal cultures were expanded by growth at 33 degrees C, differentiated by switching to a low-serum medium and growth at 39 degrees C, and screened for depolarization-induced accumulation of nitrite in the medium. The subset of putative c-NOS-positive clones (about 4%) were then screened for their expression of mRNAs using RT/PCR in combination with CE/LIF. This screening protocol proved to be powerful in the rapid isolation and phenotypic characterization of immortalized progenitor cells cloned from embryonic rat brainstem.