Use of partially phosphorothioated "antisense" oligodeoxynucleotides for sequence-dependent modulation of hematopoiesis in culture

Intra-amygdala injections of CREB antisense impair inhibitory avoidance memory: role of norepinephrine and acetylcholine

Infusions of CREB antisense into the amygdala prior to training impair memory for aversive tasks, suggesting that the antisense may interfere with CRE-mediated gene transcription and protein synthesis important for the formation of new memories within the amygdala. However, the amygdala also appears to modulate memory formation in distributed brain sites, through mechanisms that include the release of norepinephrine and acetylcholine within the amygdala. Thus, CREB antisense injections may affect memory by interfering with mechanisms of modulation, rather than storage, of memory. In the present experiment, rats received bilateral intra-amygdala infusions of CREB antisense (2 nmol/1 microL) 6 h prior to inhibitory avoidance training. In vivo microdialysis samples were collected from the right amygdala before, during, and following training. CREB antisense produced amnesia tested at 48 h after training. In addition, CREB antisense infusions dampened the training-related release of norepinephrine, and to a lesser extent of acetylcholine, in the amygdala. Furthermore, intra-amygdala infusions of the beta-adrenergic receptor agonist clenbuterol administered immediately after training attenuated memory impairments induced by intra-amygdala injections of CREB antisense. These findings suggest that intra-amygdala treatment with CREB antisense may affect processes involved in modulation of memory in part through interference with norepinephrine and acetylcholine neurotransmission in the amygdala.

Splice-switching efficiency and specificity for oligonucleotides with locked nucleic acid monomers

The use of antisense oligonucleotides to modulate splicing patterns has gained increasing attention as a therapeutic platform and, hence, the mechanisms of splice-switching oligonucleotides are of interest. Cells expressing luciferase pre-mRNA interrupted by an aberrantly spliced beta-globin intron, HeLa pLuc705, were used to monitor the splice-switching activity of modified oligonucleotides by detection of the expression of functional luciferase. It was observed that phosphorothioate 2'-O-methyl RNA oligonucleotides containing locked nucleic acid monomers provide outstanding splice-switching activity. However, similar oligonucleotides with several mismatches do not impede splice-switching activity which indicates a risk for off-target effects. The splice-switching activity is abolished when mismatches are introduced at several positions with locked nucleic acid monomers suggesting that it is the locked nucleic acid monomers that give rise to low mismatch discrimination to target pre-mRNA. The results highlight the importance of rational sequence design to allow for high efficiency with simultaneous high mismatch discrimination for splice-switching oligonucleotides and suggest that splice-switching activity is tunable by utilizing locked nucleic acid monomers.

The effect of pegylated antisense acetylcholinesterase on hematopoiesis

To determine whether the efficacy of entry and action of antisense oligonucleotides (AS-ODN) on hematopoietic stem cells in vitro could be improved by the addition of polyethylene glycol (PEG), a molecule of PEG was bound to AS- or sense-acetylcholinesterase (AS-ACHE or S-ACHE). The introduction of 0.1-0.5 microM PEG-AS-ACHE or 0.5 microM AS-ACHE into methylcellulose bone marrow (BM) cultures produced a doubling in number of colony-forming unit-granulocyte-erythrocyte-macrophage-megakaryocyte (CFU-GEMM) and a 5-fold increase in cell number of the PEG-ODN. Further increase in concentration of the PEG-ODN reduced colony numbers. PEG-AS-ACHE induced higher colony numbers and greatly increased megakaryocyte (MK) formation when compared with PEG and AS-ACHE added separately to the culture. In addition, differentials of the CFU-GEMMs indicated there was a direct relationship between MK number and PEG-AS-ACHE concentration. Under these culture conditions, 5 microM PEG alone gave control values of CFU-GEMM. On addition of FITC-PEG-AS-ACHE to the cell cultures, using confocal microscopy, the nuclei of both early and mature MKs were labeled specifically, whereas all other cellular nuclei were negative to the stain. The use of PEG-AS-ODN, affording specific delivery of AS-ODN to target cells, increased cell proliferation, and enhanced ODN uptake, may be of potential importance in stem cell expansion for BM transplantation and gene therapy.

NMR and UV studies of 3'-S-phosphorothiolate modified DNA in a DNA : RNA hybrid dodecamer duplex; implications for antisense drug design

High-resolution NMR spectroscopy has been used to establish the conformational consequences of the introduction of a single 3[prime or minute]-S-phosphorothiolate link in the DNA strand of a DNA : RNA hybrid. These systems are of interest as potential antisense therapeutic agents. Previous studies on similarly modified dinucleotides have shown that the conformation of the sugar to which the sulfur is attached shifts to the north (C(3[prime or minute])-endo/C(2[prime or minute])-exo). Comparisons made between NOESY cross-peak intensities, and coupling constants from PE-COSY spectra, for both non-modified and modified duplexes confirm that this conformational shift is also present in the double helical oligonucleotide system. In addition it is noted that in both the dinucleotides and the modified duplex, the conformation of the sugar ring 3[prime or minute] to the site of modification is also shifted to the north. That this pattern is observed in the small monomeric system as well as the larger double helix is suggestive of some pre-ordering of the sequences. The conclusion is supported by consideration of the (1)H chemical shifts of the heterocyclic bases near the site of the modification. The enhanced stability that these conformational changes should bring was confirmed by UV thermal melting studies. Subsequently a series of singly and doubly 3[prime or minute]-S-phosphorothiolate-modified duplexes were investigated by UV. The results are indicative of an additive effect of the modification with thermodynamic benefit being derived from alternate spacing of two modified linkers.

GeneBlocs are powerful tools to study and delineate signal transduction processes that regulate cell growth and transformation

The study of signal transduction processes using antisense oligonucleotides is often complicated by low intracellular stability of the antisense reagents or by nonspecific effects that cause toxicity. Here, we introduce a new class of antisense molecules, so-called GeneBlocs, which are characterized by improved stability, high target RNA specificity, and low toxicity. GeneBlocs allow for efficient downregulation of mRNA expression at nanomolar concentrations, and they do not interfere with cell proliferation. We demonstrate these beneficial properties using a positive readout system. GeneBloc-mediated inhibition of tumor suppressor PTEN (phosphatase and tension homologue detected on chromosome 10) expression leads to hyperactivation of the phosphatidylinositol (PI) 3-kinase pathway, thereby mimicking the loss of PTEN function and its early consequences observed in mammalian cancer cells. Specifically, cells treated with PTEN GeneBlocs show functional activation of Akt, a downstream effector of PI 3-kinase signaling, and exhibit enhanced proliferation when seeded on a basement membrane matrix. In addition, GeneBlocs targeting the catalytic subunit of PI 3-kinase, p110, specifically inhibit signal transduction of endogenous or recombinant PI 3-kinase. This demonstrates that GeneBlocs are powerful tools to analyze and to modulate signal transduction processes and, therefore, represent alternative reagents for the validation of gene function.

Methodologic approaches for investigating human megakaryocyte development at a molecular level

Rapid advances in defining the extracellular regulators of megakaryocyte (MK) development have heightened interest in defining the biochemical and molecular mechanisms of action of these cytokines. The recent development of molecular micromethodologies such as in situ hybridization, the polymerase chain reaction, and the use of antisense oligodeoxynucleotides now make such studies possible in normal cells. To illustrate the utility of these methods, data gathered using these methods on developing normal human hematopoietic cells and MKs is presented. As might be expected, the results obtained demonstrate that growth factors have complex time and concentration effects on gene expression in morphologically recognizable human MKs. They also suggest that a more complete understanding of normal MK development at the molecular level will soon be possible.

Complex host cell responses to antisense suppression of ACHE gene expression

3'-End-capped, 20-mer antisense oligodeoxynucleotides (AS-ODN) protected with 2'-O-methyl (Me) or phosphorothioate (PS) substitutions were targeted to acetylcholinesterase (AChE) mRNA and studied in PC12 cells. Me-modified AS-ODN suppressed AChE activity up to 50% at concentrations of 0.02-100 nM. PS-ODN was effective at 1-100 nM. Both AS-ODN displayed progressively decreased efficacy above 10 nM. In situ hybridization and confocal microscopy demonstrated dose-dependent decreases, then increases, in AChE mRNA. Moreover, labeling at nuclear foci suggested facilitated transcription or stabilization of AChE mRNA or both under AS-ODN. Intracellular concentrations of biotinylated oligonucleotide equaled those of target mRNA at extracellular concentrations of 0.02 nM yet increased only 6-fold at 1 microM ODN. Above 50 nM, sequence-independent swelling of cellular, but not nuclear, volume was observed. Our findings demonstrate suppressed AChE expression using extremely low concentrations of AS-ODN and attribute reduced efficacy at higher concentrations to complex host cell feedback responses.

Antisense oligodeoxynucleotide and ribozyme design

The overwhelming advances of the last few years in the field of nucleic acid-based technologies laid the basis for the development of this new technology as a frontier method not only to combat diseases and infections but also to study gene function. The development of antisense strategies has generated considerable expectations in the neurosciences and, in particular, behavioral neurobiology. Antisense application in the brain has become a technology with tremendous impact, especially for determining the molecular pathways and substrates of behavior of an organism controlled by independent stimuli. The antisense agents, either oligodeoxynucleotides or ribozymes, interfere in the genetic flow of information from DNA via RNA to protein. According to the literature it seems clear that appropriately modified antisense compounds successfully and stably bind to their target ribonucleic acid molecules. This antisense binding leads to a decrease in the corresponding protein levels. If the targeted protein exerts detrimental effects on the cell or tissue, its reduction should be beneficial from a therapeutic point of view. If the investigator wants to study the function of a specific gene product the selective and transient downregulation of the corresponding target protein will help in functional analysis. In the following article I describe the chemical nature of the antisense oligodeoxynucleotides and some of the most commonly used derivatives and give some guidelines on antisense construction and application. The possible mode of action is discussed, as is expansion of the oligonucleotide-based application to ribozyme-mediated gene inhibition. Finally, problems that may be encountered during antisense application are discussed.

Pharmacokinetics and in vivo effects of a six-base phosphorothioate oligodeoxynucleotide with anticancer and hematopoietic activities in swine

A short phosphorothioate oligodeoxynucleotide telomere mimic with the sequence 5'-d(TTAGGG)-3', TAG-6, has been shown to inhibit telomerase activity and have antineoplastic and hematopoietic stimulatory properties. In this study, three immature male domestic swine (weighing approximately 40 kg) were administered 200 mg/m2 of TAG-6 by continuous intravascular infusion at rates of 0.48 +/- 0.07 mg/hr for 14 days to evaluate the pharmacokinetics, toxicity, and tissue distribution. There was considerable variability (both within each animal and across animals) observed in the pharmacokinetic data. The plasma half-life (t1/2 appeared to be short enough that it could be assumed that steady state was attained by at least 96 h after the start of the infusion. The t1/2 estimates for the three pigs were 8.96, 109, and 1.97 h (the long t1/2 for pig 2 may be explained by poor parameter estimation due to the variability). The volume of distribution ranged from 9.80 to 51.8 L (0.3-1.4 L/kg), and plasma clearance estimates ranged from 0.33 to 3.46 L/h (5.5-57.7 ml/min). The average plasma concentrations at steady state were 0.845, 0.933, and 0.178 microg/ml (0.44, 0.49, and 0.093 microM) for the three animals. Nearly 30% of the administered dose was cleared through renal excretion by day 7 postinfusion. The distribution of TAG-6 was primarily to the liver and kidney, but the spleen and thyroid accumulated relatively high concentrations of TAG-6. TAG-6 was metabolized to apparently higher molecular weight products, which were observed in the urine. The size periodicity of these apparently higher molecular weight products was in 6-base intervals, which is consistent with the actions of telomerase. The infusion did not produce significant changes in serum chemistry or circulating blood cells, but a decrease in colony-forming unit-granulocyte-monocyte (CFU-GM) colony formation from BM was observed. These data suggest that TAG-6 may be a very specific pharmacophore.

Two problems in antisense biotechnology: in vitro delivery and the design of antisense experiments

Antisense oligonucleotides are invaluable reagents for the specific downregulation of gene expression. In the absence of a carrier, charged oligonucleotides (e.g., phosphorothioates) can interact with a large number of cell surface proteins, but tend to be internalized into the endosomal/lysosomal compartment. However, they can be successfully delivered to the nuclei of diverse cell types via the use of a wide variety of reagents, including cationic lipids, and cationic polyamines. Over the past several years, a more general understanding of the rules governing the interpretation of data derived from antisense experiments has been reached. These are discussed with emphasis on how to avoid some of the confounding features of this important, emerging technology.

Antisense technologies have a future fighting neurodegenerative diseases

Our growing understanding of the role that unfavorable patterns of gene expression play in the etiology of neurodegenerative disease emphasizes the need for strategies to selectively block the biosynthesis of harmful proteins in the brain. Antisense technologies are ideally suited to this purpose. Tailor-designed to target specific RNA, antisense oligonucleotides and ribozymes offer tools to suppress the production of proteins mediating neurodegeneration. Although technical limitations must still be overcome, the antisense approach represents a novel and exciting strategy for intervention in diseases of the central nervous system.

Human osteogenesis involves differentiation-dependent increases in the morphogenically active 3' alternative splicing variant of acetylcholinesterase

The extended human acetylcholinesterase (AChE) promoter contains many binding sites for osteogenic factors, including 1,25-(OH)2 vitamin D3 and 17beta-estradiol. In differentiating osteosarcoma Saos-2 cells, both of these factors enhanced transcription of the AChE mRNA variant 3' terminated with exon 6 (E6-AChE mRNA), which encodes the catalytically and morphogenically active E6-AChE isoform. In contrast, antisense oligodeoxynucleotide suppression of E6-AChE mRNA expression increased Saos-2 proliferation in a dose- and sequence-dependent manner. The antisense mechanism of action was most likely mediated by mRNA destruction or translational arrest, as cytochemical staining revealed reduction in AChE gene expression. In vivo, we found that E6-AChE mRNA levels rose following midgestation in normally differentiating, postproliferative fetal chondrocytes but not in the osteogenically impaired chondrocytes of dwarf fetuses with thanatophoric dysplasia. Taken together, these findings suggest morphogenic involvement of E6-AChE in the proliferation-differentiation balance characteristic of human osteogenesis.

Drug delivery of antisense molecules to the brain for treatment of Alzheimer's disease and cerebral AIDS

Antisense oligonucleotides (ODNs) and peptide nucleic acids (PNAs) are potential therapeutics for eradication of malignancies, viral infections, and other pathologies. However, ODNs and PNAs in general are unable to cross cellular membranes and blood-tissue barriers, such as the blood-brain barrier (BBB), which is only permeable to lipophilic molecules of molecular weight <600 Da. Cellular delivery systems based on conjugates of streptavidin (SA) and the OX26 monoclonal antibody directed to the transferrin receptor may be employed as a universal carrier for the transport of mono-biotinylated peptides, ODNs, or PNAs. 3'-Biotinylation of phosphodiester (PO)-ODN produces complete protection of ODN against serum and cellular 3'-exonucleases, facilitating the conjugation to avidin-based delivery systems and maintaining the activation of RNase H. These delivery systems markedly increased the cellular uptake and antisense efficacy of 3'-biotinylated ODNs in models of Alzheimer's disease and HIV-AIDS. In vivo brain delivery studies demonstrated that 3'-protected PO-ODNs and PO-phosphorothioate(PS)-ODN hybrids containing a single PO linkage are subjected to endonuclease degradation in vivo. On the contrary PS-ODNs, which were also protected at 3'-terminus by biotinylation, are metabolically stable in vivo and resistant to exo/endonuclease degradation. However, because of the strong binding of these oligomers to plasma protein, PS-ODNs are poorly transported into the brain through the BBB by the OX26-SA delivery vector following intravenous administration. PNAs are also resistant to exo/endonuclease and protease degradation, and these molecules biotinylated at the amino terminal group were transported into the brain by the OX26-SA delivery system with brain uptake levels comparable to that of morphine. Using the rev gene of HIV as a model target, RNase protection assays and cell-free translation arrest showed that the PNA-OX26-SA conjugate maintained active recognition and inactivation of target mRNA, respectively. The overall experimental evidence suggests that PNA-OX26-SA conjugates represent optimal antisense molecules for drug delivery to the brain.

Quantitative analysis of mRNA expression of neuron-specific growth-associated genes in rat primary neurons by competitive RT-PCR

The reverse transcriptase-polymerase chain reaction (RT-PCR) application is a sensitive method for detecting gene expression in tissues where the message level is a very small percentage of the total RNA and where only small amounts of sample are available such as in primary cultured hippocampal neurons. Based on a previously developed quantitative competitive RT-PCR strategy, mRNA expression and regulation of the neuron-specific growth-associated genes T alpha1 alpha-tubulin (T alpha1), microtubule-associated protein-2 (MAP-2) and growth-associated protein-43 (GAP-43), all of which have been proposed as putative markers of neurite growth during development and regeneration, were quantitated. This protocol, in combination with morphological evaluation of neurite outgrowth, may provide a useful tool for quantitation of neurite outgrowth during differentiation and regeneration in cultured neurons and may also be applied to detect the expression of other genes where the levels of message are low and in other tissues where small quantities of RNA are available.

Plasmodium falciparum: effect of chemical structure on efficacy and specificity of antisense oligonucleotides against malaria in vitro

Antisense oligodeoxynucleotides (AS ODNs) have shown promise both as potential anti-malarial chemotherapeutic agents and as a means for identifying genes critical for parasite survival. Because conventional ODNs containing phosphodiester (PO) groups are subject to rapid nuclease degradation, ODNs with phosphorothioate (PS) groups are commonly used. However, at high concentration, these lose target specificity, and in some animal models, they become toxic. We compared a variety of chemical modifications (PO, PS, PO-PS hybrids, 2'-O-methyl-2'-deoxy chimeras) and structural modifications (sequence alterations favoring self-stabilizing loop formation) for their ability to inhibit Plasmodium falciparum malaria cultured in vitro. All modifications were done using an AS ODN sequence targeted against dihydrofolate reductase thymidylate synthase (DHFR). Inhibition by PO-PS hybrids containing as few as three PS groups at the 3'- and 5'-ends did not differ significantly from that obtained using compounds containing all-PS groups. Similarly, inhibition by PS chimeric compounds containing 2'-O-methyl modifications did not differ significantly from that of conventional PS compounds. In contrast, while inhibition by PO-PS hybrid chimeras did not differ significantly from that of all-PS compounds at low concentrations, at 1 microM they inhibited parasite growth 25% less (P < 0.001) than all-compounds or PS 2'-O-methyl-2'-deoxy chimeras. Extension of the nucleotide sequence to increase stem-loop formation yielded two compounds which inhibited parasite growth about 20% more than unmodified compounds, though this difference was not significant. Furthermore, most of this increase appears to correlate with the greater number of PS groups associated with the increased ODN length. We conclude that limiting the number of PS groups and inclusion of PO 2'-O-methyl groups may yield compounds with high antisense activity but low non-sequence-dependent effects. Such compounds are currently being tested in vivo.

Pharmacokinetics of antisense analogues in the central nervous system

A thorough evaluation of the pharmacokinetical properties of oligodeoxyribonucleotides (ODN) is a first step towards their rational application as gene expression blockers in the central nervous system (CNS). In this paper we present our own data, as well as those of other authors, on tissue distribution, stability, retention and cellular uptake of phosphodiester, phosphorothioate, and end-capped analogues of ODN introduced into the CNS. ODN are easily distributed within nervous tissue, and their tissue penetration depends on anatomical conditions. Retention of radioactivity delivered with ODN within nervous tissue is higher for phosphodiesters than for phosphorothioates. On the other hand, the tissue stability of phosphorothioates is substantially greater than the tissue stability of phosphodiesters as well as that of end-capped ODN. If the elimination process of ODN is also due to their degradation, it is apparently accomplished by endonucleases, because the recovery of end-capped ODN (resistant to exonucleases) was similar to unprotected phosphodiesters. The uptake of ODN by nerve cells is rather poor, although we have shown that phosphorothioates at least can be internalized by nerve cells in vivo. ODN are metabolized by nerve cells, which results in the formation of unidentified molecules of higher molecular weight than ODN themselves.

Differentiation intensifies the susceptibility of pheochromocytoma cells to antisense oligodeoxynucleotide-dependent suppression of acetylcholinesterase activity

To investigate the effect of neuronal differentiation on the capacity of antisense oligonucleotides (AS-ODNs) to suppress the production of acetylcholinesterase (AChE) in rat pheochromocytoma cells, we tested seven 3'-phosphorothioated AS-ODNs targeted to ACHEmRNA and two control ODNs. Three different administration protocols were used: oligonucleotides were added at 1 microM for 24 hours to nondifferentiated PC12 cells, together with nerve growth factor (NGF) or 24 hours following NGF-induced cholinergic differentiation. The content of free thiol groups in lysed cells was measured to evaluate cell number, therefore, survival, and the rate of acetylthiocholine hydrolysis was the measure of AChE activity. Among nondifferentiated cells, over 95% survived treatment with 8 of 9 of the ODNs. Moreover, two AS-ODN suppressed AChE activity in non-differentiated PC12 cells by 16%-20% as compared with 10% suppression by control ODNs (P < or = 0.01). When added concurrently with NGF, one other AS-ODN suppressed AChE activity significantly better (28%) than the control ODNs (16%). Moreover, when added following NGF treatment, which induced a significant increase in AChE activity, four different AS-ODNs but not the control ODNs suppressed 20%-35% of the enhanced AChE activity (p < or = 0.01). Reduced levels of AChE mRNA but no difference in actin mRNA levels were observed by following the kinetics of RT-PCR amplification in differentiated PC12 cells treated with these four AS-ODNs, as compared with control cells. Our findings demonstrate a differentiation-related increase in the susceptibility of PC12 cells to inhibition by specific AS-ODNs, suggesting the use of this model system to select AS-ODNs for suppression of AChE levels in the treatment of neurodegenerative diseases associated with cholinergic malfunction.

Implication of a New Molecule IK in CD34+ Hematopoietic Progenitor Cell Proliferation and Differentiation

HLA-DR is one of the markers associated with hematopoietic cell differentiation, since expression of this molecule is modulated throughout hematopoiesis. We have previously described and cloned the gene encoding factor IK, which inhibits both interferon gamma (IFN-γ)-induced and constitutive HLA-DR expression. The current study demonstrates that IK gene transcripts are present in CD34+ cells purified from human umbilical cord blood. IK expression increased and was therefore inversely correlated with the gradual loss of HLA-DR during growth factor–induced CD34+ cell proliferation and differentiation. To study the possible role of IK in hematopoiesis, antisense probes were used. IK expression was specifically inhibited by an antisense oligodeoxynucleotide containing two phosphorothioate internucleotide linkages at each of the 3′ and 5′ ends and corresponding to the initiation site of IK mRNA. A control oligonucleotide was also tested in parallel. A specific decrease of IK transcripts was correlated with an increase of HLA-DR antigen expression level. In colony-forming assays, IK antisense oligonucleotide inhibited colony formation by multilineage early erythroid and granulomonocytic CD34+ progenitors. The mean colony size was decreased 70% by IK antisense oligonucleotide in comparison to controls. These results provide evidence that the IK molecule participates in the regulation of HLA-DR expression on hematopoietic cells and plays a role in growth factor–dependent CD34+ cell proliferation and differentiation by modulating HLA-DR expression.

Implication of a New Molecule IK in CD34+ Hematopoietic Progenitor Cell Proliferation and Differentiation

HLA-DR is one of the markers associated with hematopoietic cell differentiation, since expression of this molecule is modulated throughout hematopoiesis. We have previously described and cloned the gene encoding factor IK, which inhibits both interferon gamma (IFN-γ)-induced and constitutive HLA-DR expression. The current study demonstrates that IK gene transcripts are present in CD34+ cells purified from human umbilical cord blood. IK expression increased and was therefore inversely correlated with the gradual loss of HLA-DR during growth factor–induced CD34+ cell proliferation and differentiation. To study the possible role of IK in hematopoiesis, antisense probes were used. IK expression was specifically inhibited by an antisense oligodeoxynucleotide containing two phosphorothioate internucleotide linkages at each of the 3′ and 5′ ends and corresponding to the initiation site of IK mRNA. A control oligonucleotide was also tested in parallel. A specific decrease of IK transcripts was correlated with an increase of HLA-DR antigen expression level. In colony-forming assays, IK antisense oligonucleotide inhibited colony formation by multilineage early erythroid and granulomonocytic CD34+ progenitors. The mean colony size was decreased 70% by IK antisense oligonucleotide in comparison to controls. These results provide evidence that the IK molecule participates in the regulation of HLA-DR expression on hematopoietic cells and plays a role in growth factor–dependent CD34+ cell proliferation and differentiation by modulating HLA-DR expression.

Development of targeted delivery systems for nucleic acid drugs

Our increased understanding of disease pathogenesis is the basis for developing novel nucleic acid drugs. The main challenge encountered in this development is how to maintain therapeutically meaningful concentrations of the drugs in the vicinity of their targets for the desired periods. The intrinsic difficulty arises from the fact that nucleic acid drugs are not readily transported across membranes. Hence, their delivery and transport characteristics at the whole body, organ and cellular levels need to be thoroughly examined. Liposomes and receptor-mediated polycation systems are promising carriers for their delivery in vivo. There are many barriers to be overcome for successful antisense and gene therapies. Along with other factors, disposition, stability against nucleases, binding to cell surface receptor and internalization, and intracellular trafficking affect the in vivo delivery and efficacy of nucleic acid drugs. This review article discusses the delivery and transport of these compounds.

Dopaminergic regulation of progesterone receptors: brain D5 dopamine receptors mediate induction of lordosis by D1-like agonists in rats

To characterize the signaling pathway by which the neurotransmitter dopamine modulates progesterone receptor (PR) activation, the steroid-dependent behavior lordosis was used in estrogen-primed ovariectomized Sprague-Dawley rats with stereotaxic implanted third ventricle cannulas. Lordosis was observed in response to solicitous males in females after central administration of the D1-like agonist SKF38393 and three of its analogs (SKF77434, SKF75640, and SKF85174). In contrast, D1-like antagonist SCH23390 and D1-like/D2 repopulation inhibitor EEDQ blocked behavior inducible by the D1-like agonists. Further, antisense oligonucleotides to D5, but not D1, dopamine receptor mRNA suppressed reproductive behavior associated with D1-like stimulation. This finding provides strong evidence that dopaminergic modulation of lordosis is mediated by the novel D5 dopamine receptor. Although D1, but not D5, dopamine receptor mRNAs were detected in the ventromedial nucleus (VMN) by in situ hybridization, agonists microinjected into the VMN, but not into the arcuate nucleus or preoptic area, induced lordosis, suggesting the functional presence of D5 dopamine receptors in the VMN. Also in support, D5 receptor mRNA antisense microinjected into the VMN blocked the subsequent induction of lordosis by D1-like agonists. Finally, facilitation of sex behavior by D1-like agonists was blocked by the antiprogestin RU38486 and PR antisense oligonucleotide. Collectively, the data provide strong evidence for dopaminergic modulation of reproductive behavior through D5 dopamine receptor-mediated modulation of PR-dependent behavior in rat CNS.

Non-classical actions of cholinesterases: role in cellular differentiation, tumorigenesis and Alzheimer's disease

The cholinesterases are members of the serine hydrolase family, which utilize a serine residue at the active site. Acetylcholinesterase (AChE) is distinguished from butyrylcholinesterase (BChE) by its greater specificity for hydrolysing acetylcholine. The function of AChE at cholinergic synapses is to terminate cholinergic neurotransmission. However, AChE is expressed in tissues that are not directly innervated by cholinergic nerves. AChE and BChE are found in several types of haematopoietic cells. Transient expression of AChE in the brain during embryogenesis suggests that AChE may function in the regulation of neurite outgrowth. Overexpression of cholinesterases has also been correlated with tumorigenesis and abnormal megakaryocytopoiesis. Acetylcholine has been shown to influence cell proliferation and neurite outgrowth through nicotinic and muscarinic receptor-mediated mechanisms and thus, that the expression of AChE and BChE at non-synaptic sites may be associated with a cholinergic function. However, structural homologies between cholinesterases and adhesion proteins indicate that cholinesterases could also function as cell-cell or cell-substrate adhesion molecules. Abnormal expression of AChE and BChE has been detected around the amyloid plaques and neurofibrillary tangles in the brains of patients with Alzheimer's disease. The function of the cholinesterases in these regions of the Alzheimer brain is unknown, but this function is probably unrelated to cholinergic neurotransmission. The presence of abnormal cholinesterase expression in the Alzheimer brain has implications for the pathogenesis of Alzheimer's disease and for therapeutic strategies using cholinesterase inhibitors.

Investigation of the intracellular stability and formation of a triple helix formed with a short purine oligonucleotide targeted to the murine c-pim-1 proto-oncogene promotor

In our previous work we have shown that the oligonucleotide 5'-GGGGAGGGGGAGG-3' gives a very stable and specific triplex with the promoter of the murine c-pim-1 proto-oncogene in vitro[Svinarchuk, F., Bertrand, J.-R. and Malvy, C.(1994)Nucleic Acids Res., 22, 3742-3747]. In the present work, we have tested triplex formation with some derivatives of this oligonucleotide which are designed to be degradation-resistant inside the cells, and we show that phosphorothioate and the oligonucleotide with a 3' terminal amino group are still able to form triplexes. Moreover these oligonucleotides, like the 13mer oligonucleotide of similar composition [Svinarchuk, F., Paoletti, J., and Malvy, C. (1995) J. Biol. Chem., 270, 14068-14071], are able to stabilize the targeted duplex. In vivo DMS footprint analysis after electroporation of the pre-formed triplex into the cell have shown the presence of the triple helix inside the cells. This triplex structure partially blocks c-pim-1 promotor activity as shown by transient assay with a c-pim-1 promoter-luciferase gene construct. To our knowledge these data are the first direct evidence that conditions inside cells are favorable for triplex stability with non-modified oligonucleotides. However we were unable to show triplex formation inside living cells using various methods of oligonucleotide delivery. We suppose that this may be due to the oligonucleotide being sequestered by cellular processes or proteins. Further work is needed to find oligonucleotide derivatives and ways of their delivery to overcome the problem of triplex formation inside the cells.

Antisense inhibition of butyrylcholinesterase gene expression predicts adverse hematopoietic consequences to cholinesterase inhibitors

1. To investigate the possibility that cholinesterase inhibitors may cause adverse hematopoietic effects, we employed antisense oligodeoxynucleotides selectively inhibiting butyrylcholinesterase gene expression (AS-BCHE). Complementary sense (S) oligonucleotides served as controls. 2. In primary bone marrow cell cultures grown with interleukin 3 (IL-3), AS-BCHE but not S-BCHE reduced growth of megakaryocyte colony-forming units (CFU-MK) in a dose-dependent manner at the micromolar range. 3. In cultures grown with IL-3, transferrin, and erythropoietin (Epo), cell counts increased up to twofold, yet colony counts (CFU-GEMM) remained unchanged under AS-BCHE treatment. 4. Electrophoretic measurements of DNA ladder as an apoptotic index revealed that the above oligonucleotide effects were not due to nonspecific induction of programmed cell death. 5. Differential cell counts demonstrated increased myeloidogenesis and reduced levels of early megakaryocytes in CFU-GEMM under AS-BCHE, suggesting requirement of the BuChE protein for megakaryopoiesis. 6. In vivo injection of AS-BCHE reduced BCHE mRNA levels in both young and mature megakaryocytes for as long as 20 days, as shown by in situ hybridization. 7. Ex vivo growth of primary bone marrow cells revealed a twofold reduction in CFU-MK colonies grown from the AS-BCHE- but not the S-BCHE-injected mice, 15 days posttreatment. 8. These findings demonstrate that deficient butyrylcholinesterase expression, and hence interference with this enzyme's activity through treatment with or exposure to cholinesterase inhibitors, may cause hematopoietic differences in treated patients.