Antisense oligonucleotides inhibit gene expression by interfering with transcription, translation, or splicing. They show great potential as gene-specific, nontoxic therapy for a wide variety of diseases. They are also powerful tools to study gene function as well as for validation of therapeutic targets. Even with compelling evidence of activity in vivo, the majority of cell types in culture require technologies capable of efficiently delivering antisense oligonucleotides into the cytosolic/nuclear compartment of the cells in culture. Phosphorodiamidate morpholino oligomers (PMO) are a new generation of antisense oligomers with high specificity and efficacy. They inhibit translation of targeted mRNA by steric blockade. Different methods were evaluated for efficient delivery of PMO into the cells in culture. Efficacy was compared using the PMO targeted to the 5'-untranslated region (5'-UTR) of alpha-globin-luciferase reporter fusion gene mRNA. A functional assay based on the lunciferase reporter system was used to measure efficacy. The fluorescence-activated cell sorting (FACS) method was used for quantitative determination of PMO uptake into the cells. Physical methods, such as scrape-loading, syringe-loading, and osmotic-loading, provided efficient transfer of PMO into the cells, which resulted in higher efficacy. These procedures caused minimal damage to the cells. Cell permeabilization with streptolysin O did not improve the cell uptake of PMO. Complexation with cationic lipids, Lipofectin and Lipofectamine (GIBCO-BRL, Gaithersburg, MD) also failed to enhance the uptake of PMO. We conclude that physical methods are optimal for the delivery of neutrally charged PMO into cells in culture. Further, these methods do not leave residual material that may interfere with the interpretation of targeted gene function.

ZF-L cells were derived from normal adult zebrafish liver, and have been growing in culture for more than 100 generations. The cells were derived in basal nutrient medium supplemented with fetal bovine serum (FBS), trout serum, trout embryo extract, bovine insulin and mouse epidermal growth factor. After 50 generations in culture, optimal growth of the cells was achieved in medium supplemented with FBS (5%) and trout serum (0.5%). ZF-L cells were hypodiploid (modal chromosome number = 46) and exhibited an epithelial morphology. ZF-L cell homogenates exhibited alanine and aspartate aminotransferase, glucose-6-phosphatase and alkaline phosphatase enzyme activities. The cells synthesized and released several proteins into the culture medium, including a 70 kDa protein recognized by anti-bovine serum albumin IgG.

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Nitric oxide (NO) is an unstable radical produced during the oxidative deamination catalyzed by NO synthase (NOS) that converts L-arginine to L-citrulline. NO is also generated nonenzymatically from a group of compounds, called NO donors, such as sodium nitroprusside (SNP). NO directly or through its metabolites has been implicated in several disorders, including Alzheimer's disease (AD). Since NO is a highly labile unstable free gas, we measured the stable end products, nitrite and nitrate (NOx). Here, we investigated the effect of SNP-mediated NO release in different cell types and its effect on the beta-amyloid precursor protein (betaAPP). When different cell types were induced with SNP, a significant level of NOx was detected in a time and dose-dependent manner over the spontaneous release of NOx by SNP. The astrocytes, glial, and epithelial cell lines released significantly higher level of NOx as compared to neuronal cells following the exposure of SNP. The latter group of cells was more sensitive to NO-mediated cytotoxicity, as demonstrated by the lactate dehydrogenase assay. The SNP-mediated toxicity is known to be caused by the accumulation of cyanide ions and we report that the ability of cells to protect against it depends on the levels of nitric oxide metabolites. Cell lines, such as astrocytic and epithelial, that produce more NOx are better protected against the SNP-induced toxicity than the less NOx-protecting neuronal cell lines. The possibility of differential susceptibility of neurons and astrocytes resulting from the different content of reduced glutathione is also discussed. The release of NOx was prevented by cotreatment with a NO scavenger and superoxide dismutase but not by a NOS inhibitor. The activity of NOS was decreased when cytosolic extracts were incubated with SNP. In the conditioned medium of SNP-induced cells, the level of soluble betaAPP (sAPP) was decreased, and this decrease was more apparent in neuronal than astrocytic cell lines. Taken together, these results suggest that the SNP-derived NO release is independent of the NOS pathway, that various cell types metabolize SNP differently, and that neuronal cell lines are more vulnerable with SNP treatment with lowered sAPP secretion. Since the neuronal cell lines lack a nitric-oxide-generated protective mechanism, we speculate that these cells may be the first targets of neurodegeneration by several toxic agents, including the cyanides and peroxynitrites.

Accumulation of reactive oxygen species is critical for the neuropathology of Alzheimer's disease. Melatonin hormone, an antioxidant, could play a key role in aging and senescence. Nitric oxide, a biologically active unstable radical, is synthesized by nitric oxide synthase when converting L-arginine to L-citrulline. We have investigated whether the treatment of cultured cells with melatonin could possibly reduce the release of free radicals and other ROS. We assayed NO indirectly by measuring the level of its stable end products, nitrite/nitrate (NOx), using the Griess reagent. When the neuroblastoma cells such as N1E-115 were treated with a NO donor such as sodium nitroprusside (SNP), a significant level of NOx was detected in a time- and dose-dependent manner in the conditioned medium compared to the untreated cells or SNP-containing media. In neuroblastoma cells, the release of NOx as mediated by SNP was significantly inhibited by treatment with (i) carboxy-PTIO, a NO scavenger; (ii) SOD-1, superoxide dismutase; and (iii) melatonin. In these cells SNP-mediated NOx release was mediated by superoxide ions and/or free radicals that can be inhibited by melatonin. The ROS-scavenging function of melatonin along with its neuroprotective and neurodifferentiating role can be utilized for the prevention of neurodegenerative disorders such as AD.