Examination of antisense RNA and oligodeoxynucleotides as potential inhibitors of avian leukosis virus replication in RP30 cells

Avian leukosis virus (ALV) is an economically important pathogen of chickens. Both antisense RNA and antisense oligodeoxynucleotides (ODN) have been used to diminish the replication and spread of other retroviruses. The use of antisense RNA and ODN to inhibit ALV replication has been examined in cultured RP30 cells. Using an expression system that constitutively transcribes antisense ALV RNA, one transfected cell clone showed a significant reduction in virus growth. However, this effect was not reproducibly observed in other transfected cell lines or in cells in which the antisense transcript was expressed from a regulatable promoter, even though a substantial amount of antisense transcript was generated. Antisense ODN complementary to several different target sites near the 5' end of the ALV genome were also tested for antiviral activity, by comparison of antisense ODN effects to those of randomized sequence controls. An antisense ODN complementary to the ALV primer binding site demonstrated a reproducible reduction in viral replication. However, when the corresponding region was specifically employed as a target for intracellular antisense RNA expression, there again was no significant inhibition of ALV. These results suggest that in vivo expression of antisense RNA is unlikely to be an effective way to generate transgenic poultry that are resistant to field strains of ALV.

Malaria merozoite surface protein antisense oligodeoxynucleotides lack antisense activity but function as polyanions to inhibit red cell invasion

The effects on malaria parasite growth of antisense and sense oligodeoxynucleoside phosphorothioates based on a merozoite surface protein mRNA was examined. Specific antisense effects of the oligonucleotides could not be demonstrated over three cycles of schizogony or when added as a complex with cationic liposomes. Antisense and sense oligonucleotides however, inhibit merozoite invasion of red blood cells at similar concentrations to dextran sulphate, a polyanion, as determined by microscopy and [3H]hypoxanthine incorporation into DNA. Neutralisation of the negative charge on the oligonucleotides by binding to cationic lipid liposomes, prevented the inhibition of merozoite invasion. We postulate that oligonucleotides because of their polyanionic nature interfere with the binding of merozoites to receptors on red blood cells and that polyanions may be useful in malaria therapy.

[Inhibition of apoptosis by bcr-abl fusion gene in K562 cells]

OBJECTIVE

To investigate the effect of bcr-abl fusion gene on CML cell apoptosis.

METHODS

Apoptosis of in vitro cultured K562 cells was observed after exposure to synthetic 18-mer antisense oligodeoxynucleotide complementary to the bcr-abl junction (b3a2).

RESULTS

Apoptosis of K562 cells was significantly increased associated with inhibition of bcr-abl expression.

CONCLUSION

bcr-abl fusion gene formation due to chromosome translocation may be the major mechanism of CML via inhibition of apoptosis.

Effect of antisense mitogen-activated protein kinase oligonucleotides on rat vascular smooth muscle cell proliferation induced by EGF in vitro

AIM

To study the preventive effect of down-regulating mitogen-activated protein kinase (MAPK) on vascular smooth muscle cell (VSMC) proliferation.

METHODS

Cultured rat VSMC was pretreated with a phosphorothioate-protected 17-mer antisense MAPK oligodeoxynucleotides (ODN) directed against the initiation of translation sites of the p42- and p44-MAPK isoforms by liposomal transfection. A 17-mer sense and a random sequence MAPK ODN were used as control. After liposomal transfection, cells were exposed to epidermal growth factor (EGF) 1 nmol.L-1 for 10 min and then harvested in lysis buffer. MAPK activity was measured by Western blot and P-81 phosphocellulose filter papers method by using [gamma-32P] ATP and myelin basic protein as substrate. DNA synthesis was measured by [3H]thymidine incorporation.

RESULTS

Antisense ODN 0.2 mumol.L-1 reduced EGF-induced MAPK activities by 84%, and inhibited VSMC [3H]thymidine incorporation stimulated by EGF.

CONCLUSION

A 17-mer MAPK antisense oligonucleotide directed against the initiation of translation sites of the p44- and p42-MAPK inhibited EGF-stimulated rat VSMC proliferation.

Central administration of dopamine D3 receptor antisense to rat: effects on locomotion, dopamine release and [3H]spiperone binding

A 15-mer, all-phosphorothioate-modified antisense oligodeoxynucleotide (ASO) targeted against rat dopamine D3 receptor mRNA (4 microM, 5 days) significantly reduced (28%) the amount of binding sites labelled with [3H]spiperone in monolayer cultured Chinese hamster ovary (CHO) cells transfected with the complementary desoxyribonucleic acid (cDNA) for the rat D3 receptor. In contrast, D3-ASO treatment did not reduce the amount of bound [3H]spiperone in CHO cells transfected with D2 receptor cDNA. Intracerebroventricular infusion of D3-ASO (osmotic minipump, 10 microg/microl/h, 7 days) influenced dopamine receptor density in the limbic forebrain such that the upper part of the dopamine/[3H]spiperone displacement curve--tentatively representing the D3 receptor--was altered significantly. Spontaneous locomotor activity of non-habituated rats was increased significantly in D3-ASO-treated animals; in addition, in vivo microdialysis revealed a moderate increase in dopamine release in the nucleus accumbens in these animals. In all experiments, an oligodeoxynucleotide comprising the same nucleotides as the antisense sequence, but in random order, was used as control. It is concluded that the antisense strategy is useful for investigating the functional role of dopamine D3 receptors and that the dopamine D3 receptor is involved in rat locomotor behaviour.

Antisense to MDR1 mRNA reduces P-glycoprotein expression, swelling-activated C1- current and volume regulation in bovine ciliary epithelial cells

Native ciliary epithelial cells from the ciliary epithelium of the eye exhibit anti-P-glycoprotein (P-gp) immunofluorescence. We have used an antisense 'knock-down' approach to investigate the relationship between P-gp and the volume-activated chloride current (IC1,swell) and its role in volume regulation. An antisense oligonucleotide to the human multidrug resistance (MDR1) gene, taken up by the cells in a dose-dependent manner, reduced P-gp immunofluorescence, inhibited IC1,swell and significantly increased the latency of activation of IC1,swell. Increasing the hypotonic stress did not result in an increased activation of ICl,swell. MDR1 antisense 'knock-down' also reduced the ability of the cells to volume regulate following a hypotonic challenge. These cells are known to express at least two volume-activated chloride channels, and the data suggest that P-gp is involved in the activation pathway of a subset of channels that contribute to whole-cell IC1,swell and participate in volume regulation.

Growth inhibition of pancreatic tumor cells by modified antisense oligodeoxynucleotides

INTRODUCTION

Pancreatic adenocarcinomas are largely resistant to apoptosis. More than 50% of pancreatic tumors reveal mutations in the p53 tumor suppressor gene.

METHODS

We investigated the growth of pancreatic tumor cells after downregulation of p53 protein expression by antisense oligodeoxynucleotides.

RESULTS

Proliferation and p53 expression of PancTu-I cells overexpressing mutant p53 protein were inhibited by antisense oligodeoxynucleotide treatment. When analyzed, two of three other pancreatic tumor cell lines with mutated p53 were also inhibited in their growth. Two of two wild-type (wt) p53 pancreatic tumor cells were not significantly influenced by p53 expression and were, only to a lesser extent, affected in their proliferation. K562 cells (lacking p53 mRNA) and normal human skin fibroblasts used as a target mismatch control showed no changes in proliferation rates with treatment. The different biological effects in the various cells were not caused by differences in the uptake of the oligodeoxynucleotides as monitored by confocal laser-scanning microscopy.

CONCLUSIONS

Truncation and 5'- and 3'-lipophilic modifications of the oligodeoxynucleotides drastically enhanced the growth inhibition of PancTu-I cells, which were resistant to apoptosis-inducing agents. Furthermore, a higher sequence-specificity of the observed effects was achieved with these compounds.

Effect of antisense oligodeoxynucleotides directed to individual calmodulin gene transcripts on the proliferation and differentiation of PC12 cells

Calmodulin (CaM) is encoded by three different genes that collectively give rise to five transcripts. In the present study, we used antisense oligodeoxynucleotides targeted to unique sequences in the transcripts from the individual CaM genes to selectively block the expression of the different genes and to investigate the roles these individual genes play in the proliferation and nerve growth factor (NGF)-induced differentiation of PC12 cells. Culturing PC12 cells in the presence of oligodeoxynucleotide antisense to the transcripts from CaM genes I and II caused a significant decrease in the proliferation and a significant delay in the NGF-induced differentiation of PC12 cells when compared with untreated cells and with cells treated with the corresponding randomized oligodeoxynucleotides. However, an oligodeoxynucleotide antisense to CaM gene III did not significantly alter the proliferation or the NGF-induced differentiation of PC12 cells. The inhibition of cell proliferation could be reversed by washing out the antisense oligodeoxynucleotides. The levels of CaM in cells treated with oligodeoxynucleotides antisense to CaM genes I or II were reduced 52% or 63%, respectively, of the levels found in the control cells. However, the levels of CaM were not significantly reduced in PC12 cells treated with CaM gene III antisense oligodeoxynucleotide. None of the randomized oligodeoxynucleotides had any effect on the levels of CaM in PC12 cells. The reduced levels of CaM in PC12 cells treated with an oligodeoxynucleotide antisense to CaM gene I were accompanied by a reduction in the levels of the CaM gene I mRNAs, supporting a true antisense mechanism of action for these oligodeoxynucleotides. These results suggest that altering the level of CaM by using antisense oligodeoxynucleotides targeted to the dominant CaM transcripts in a particular cell type will specifically inhibit their proliferation and, in the case of neuronal cells, alter the course of their differentiation.

Antisense depletion of beta-subunits fails to affect T-type calcium channels properties in a neuroblastoma cell line

Voltage-gated calcium channels can be classified into high voltage activated (HVA) and low voltage activated (LVA or T-type) subtypes. The molecular diversity of HVA channels primarily results from different genes encoding their pore-forming alpha1 subunits. These channels share a common structure with an alpha1 subunit associated with at least two regulatory subunits (beta, alpha2-delta). Any of the six alpha1-related channels identified to date are regulated in their functional properties through an interaction with the ancillary beta-subunit. By contrast, the diversity and the molecular identity of LVA or T-type calcium channels have yet to be defined. Whether LVA channels are modulated by a beta-subunit, like HVA channels, is unknown. To address this issue, we have used an antisense strategy to inhibit beta-subunit expression in the NG 108-15 neuroblastoma cell line. Differentiated NG 108-15 cells express both LVA and HVA channels. We found that LVA currents were unaffected when cells were incubated with beta-antisense, while HVA currents were drastically decreased. Since LVA Ca channel currents in NG 108-15 cells are not regulated by beta-subunits, it is reasonable to postulate that the pore-forming subunit(s) of these channels lacks an interaction domain with a beta-subunit (AID). This molecular feature, which is common to various T-type channels, indicates further that LVA calcium channels belong to a channel family structurally distant from HVA channels.

[Antisense oligodeoxynucleotide of TGF alpha inhibits its gene expression and proliferation of a human glioma cell line]

OBJECTIVE

To study the effect of antisense oligodeoxynucleotide(ON) of TGF alpha on its gene expression in TJ 905 cell line.

METHODS

Antisense and sense TGF alpha phosphorothioate ON (SON) and random SON were synthesized and transfected to TJ 905 cells mediated by lipofectin. Their effects on the TGF alpha gene expression were examined by in situ hybridization of TGF alpha mRNA, immunohistochemical study and cell count.

RESULTS

(1) TGF alpha antisense SON could significantly inhibit the growth of TJ 905 cell line. The inhibition peaked at 24 hour after transfection, the inhibition rate reached 68% at 20 microM, and the effect decreased 72 hours after transfection. The inhibition effect was dose dependent. (2) Antisense TGF alpha SON inhibited TGF alpha expressions at both mRNA and protein levels.

CONCLUSION

Antisense TGF alpha SON can inhibit the expressions of TGF alpha and markedly inhibit cell growth of human glioma TJ 905 cell line. TGF alpha contributes in the growth potential of glioma.

[The effect of c-myc antisense oligodeoxynucleotides on proliferation of pulmonary arterial smooth muscle cells stimulated by hypoxic endothelial cells conditioned medium]

OBJECTIVE

To study the effect of c-myc antisense oligodeoxynucleotides on proliferation of pulmonary arterial smooth muscle cells (SMC) stimulated by hypoxic endothelial cells conditioned medium (HECCM).

METHOD

After pulmonary arterial SMC were stimulated by HECCM, Northern blot technique was used for detection of expression of c-myc, and 3H-TdR incorporation and cell growth assay for detection of proliferation of SMC.

RESULT

HECCM promoted the expression of c-myc and proliferation of SMC significantly. Antisense-ODNs significantly inhibited the expression of c-myc and proliferation of SMC stimulated by HECCM, whereas sense ODNs didn't affect the expression of c-myc and proliferation of SMC.

CONCLUSION

HECCM promote the proliferation of SMC by increasing the expression of c-myc, antisense ODNs inhibits the proliferation of SMC by downregulating the expression of c-myc gene.

[Antisense oligodeoxynucleotide targeted at the pre-s region of DHBV could inhibit virus replication in vivo]

To study the antiviral effect of antisense oligodeoxynucleotide (AS-ODN), AS-ODN phosphotioates targeted to DHBV Pre-S region (951-968nt) (5'-TATCTCCTCCATTGTTTG-3') was synthesized. Two day-old ducklings were infected i.p. with 150 microliters of DHBV (3 x 10(8) copies/ml DHBV). After 12 days, 6 DHBsAg and DHBV DNA positive ducks were divided into two groups. In treated group, each duck was injected i.v. AS-ODN 20 micrograms/gram weight/day for 10 dyas successively, while in the control group, each duck received the same volume of normal saline for 10 days. Sera from ducks prior to treatment and treated after 6, 10 days were collected, and after 10 days ducks were sacrificed and livers were examined. DHBsAg was significantly decreased in all three treated ducks after 10 days of AS-ODN treatment. One of these ducks showed decreased DHBsAg even 6 days after treatment. Two out of three treated ducks showed decreased serum DHBV DNA, while one remained unchanged. In contrast, none of the control group showed decreased DHBsAg and DHBV DNA did not change. By Southern blot, DHBV DNA in the liver significantly decreased in 2/3 of the treated ducks and decreased in the other duck. In all control ducks, DHBV DNA remained strongly positive. Data indicated that AS-ODN targeting at Pre-S region could partly inhibit the replication of DHBV.

[Inhibitive effect of bcl-2 antisense oligodeoxynucleotide on Bcl-2 protein synthesis and cell proliferation in human laryngocarcinoma Hep-2 cells]

OBJECTIVES

To evaluate the role of bcl-2 antisense oligodeoxynucleotide in the gene treatment of human laryngocarcinoma.

METHODS

An antisense oligodeoxynucleotide complementary to the initiation coden and the next four codens of bcl-2 mRNA was synthesized with an automatic DNA synthesizer. It was used to treat cultured Hep-2 cells to observe its effect on cell proliferation. In situ hybridization method and immunohistochemical technology were adopted to detect bcl-2 mRNA and protein and explore the effect of bcl-2 antisense oligodeoxynucleotide fragment on bcl-2 gene expression and protein synthesis and inhibition of cell proliferation.

RESULTS

Bcl-2 antisense oligodeoxynucleotide had an obvious effect on bcl-2 mRNA, but inhibited Bcl-2 protein synthesis significantly, the inhibitive rate had positive correlation with concentration of antisense oligodeoxynucleotide and time of action. Twenty mumol/L of antisense oligodeoxynucleotide could inhibit cell proliferation effectively.

CONCLUSIONS

It is suggested that bcl-2 antisense oligodeoxynucleotide might specifically inhibit bcl-2 protein synthesis and cell proliferation in Hep-2 cells at translation level.

Mu receptor and Gi2alpha antisense attenuate [D-Met2]-FMRFamide antinociception in mice

FMRFamide (Phe-Met-Arg-Phe-NH2) and several analogs produce centrally-mediated, naloxone-reversible antinociception, but have minimal affinity for opioid receptor (sub)types. In the present study, the antinociception in mice (55 degrees C tail-flick test) produced by supraspinal (intracerebroventricular; i.c.v.) administration of [D-Met2]-FMRFamide (a stable analog of FMRFamide) was attenuated by pretreatment with i.c.v. oligodeoxyribonucleotide antisense to the opioid mu receptor or by antisense to the Gi2alpha G-protein subunit. These data suggest that [D-Met2]-FMRFamide produces its antinociception via an opioid interneuron.

[The inhibitory effect of combined treatment of TNF alpha and antisense oligodeoxynucleotides on the growth of human pancreatic carcinoma cell line cells]

OBJECTIVE

To study the inhibitory effect induced by combined treatment of TNF alpha and antisense oligodeoxynucleotide on the growth of human pancreatic adenocarcinoma cell line (PC-2) cells.

METHOD

TNF alpha and synthesized antisense c-myc or Ki-ras phosphorothioate oligodeoxynucleotide (ASPODN) were added to the culture media of PC-2 cells, whereas the groups treated with TNF alpha or ASPODN alone were used as controls. The cell growth rate was estimated by cell count and MTT analysis, the endogenous target gene expression was studied by adopting RT-PCR-Southern blot technique, and cell apoptosis was detected in situ.

RESULTS

The cell growth was inhibited much more obviously in the groups of combined treatment than in the groups treated with TNF alpha or ASPODN alone. Marked inhibition of endogenous Ki-ras and c-myc expression was observed in the groups treated with Ki-ras and c-myc ASPODN. The amounts of apoptotic cells were 8.0% and 8.4% in the groups of TNF alpha + Ki-ras ASPODN and TNF alpha + c-myc ASPODN, and were 5.2%, 4.8% and 5.4% for TNF alpha, Ki-ras ASPODN and c-myc ASPODN respectively.

CONCLUSION

Our results demonstrate that the inhibitory effect induced by combined treatment of TNF alpha and ASPODN on cell growth was stronger than that induced by TNF alpha or ASPODN alone.

[Inhibition of cell growth and target gene expression of human pancreatic carcinoma cells by modified antisense oligodeoxynucleotide]

OBJECTIVE

To investigate the inhibitory effects of modified antisense oligodeoxynucleotide on cell growth, 3H-TdR incorporation rate and target gene expressions of human pancreatic carcinoma cells as a comparison with the effectiveness of nonmodified antisense oligodeoxynucleotide (ASODN) resported previously.

METHODS

Synthesized modified antigsense oligodeoxynucleotides (antisense phosphorothioate oligodeoxynucleotides, ASPODN) complementary to the cap regions of c-myc and Ki-ras genes were used to treat PC-2 and PC-3 human pancreatic carcinoma cell line cells with multiple small (10 micrograms) doses or one single dose (15 micrograms). After treatment, cell growth rates and 3H-TdR incorporation rates were estimated, and the concurrent oncogene expressions were studied by adopting RT-PCR technique.

RESULTS

After multiple ASPODN exposures, the cell growth rates and 3H-TdR incorporation rates were significantly inhibited, the inhibition was maintained for more than two weeks. On the 14th day, the cell growth rates of the ASPODN groups were reduced to 38%-43% of that of the controls, and the 3H-TdR incorporation rates were 18%-33% of that of the controls, there were also marked inhibition or down-regulation of target genes (c-myc and Ki-ras) expressions. After the 15 micrograms single dose treatment, the inhibition of cell growth, 3H-TdR incorporation and target gene expressions lasted for 4 days.

CONCLUSIONS

The results of this study confirm the fact that ASPODN exerts a more strong inhibitory effect on pancreatic carcinoma cells than the non-modified ASODN.

[Antiviral effect of antisense oligodeoxynucleotides complementary to hepatitis B virus X gene in vitro]

It has been reported that the products of the human hepatitis B virus (HBV) X genes can transactivate a variety of viral and host promoters including the X, core, pre S2/S and pre S1 promoter. In order to investigate their antiviral effect in cell culture, three pieces of antisense phosphorothioate oligodeoxynucleotides (ASON) complementary to HBV X genes 1510-1530, 1555-1581, 1768-1791 regions were synthesized. The specificity of the inhibitory effect of the ASON was determined by using 2, 2, 15 cells by ELISA, PAP-ELISA and in situ hybridization to detect HBsAg, HBeAg, HBxAg and HBV DNA. The results showed that these ASON could inhibit the expression of HBxAg, as well as HBsAg and HBeAg, with the inhibitary rates of 78.07%, 80.65% and 62.76% respectively. In situ hybridization results indicated that HBV DNA replication can also be inhibited. The decrease in virus production and the ammount of HBV DNA were dose and time dependent. The mechanism of action may be due to the inhibition of HBxAg by sequences specific to ASON, and then the decrease of its transactivating effect for HBV DNA promoter.

Functional roles of dopamine D2 and D3 autoreceptors on nigrostriatal neurons analyzed by antisense knockdown in vivo

Two different 19-mer antisense oligodeoxynucleotides complementary to the initial coding regions of dopamine D2 or D3 receptor mRNA were infused unilaterally into the substantia nigra of rats for 3-6 d to suppress synthesis of D2 and/or D3 receptors on substantia nigra dopaminergic neurons, thereby producing specific reductions of D2 and/or D3 receptors. Autoradiographic receptor binding revealed that D2 and D3 antisense oligodeoxynucleotides specifically and significantly reduced D2 or D3 binding in the ipsilateral substantia nigra, respectively, without affecting dopamine receptor binding in the neostriatum. Either D2 or D3 antisense oligodeoxynucleotides greatly attenuated the ability of apomorphine to inhibit dopaminergic neurons in vivo, an effect that was potentiated by simultaneous administration of D2 and D3 antisenses. Despite these effects, neither the rate nor the pattern of spontaneous activity of antisense-treated nigrostriatal neurons differed from those in the control groups. The proportion of antidromic responses consisting of full spikes from antisense-treated rats was significantly greater, and the mean antidromic threshold was significantly lower than in controls, indicating that autoreceptor knockdown increased both somatodendritic and terminal excitability. These data demonstrate that selective reduction of specific dopamine receptor subtypes by antisense infusion can be effected in vivo, and that nigrostriatal neurons express both D2 and D3 autoreceptors at their somatodendritic and axon terminal regions. Although the somatodendritic and terminal autoreceptors modulate dendritic and terminal excitability, respectively, the interaction of endogenously released dopamine with somatodendritic autoreceptors does not appear to exert a significant effect on spontaneous activity in anesthetized rats.