S-isobutyl Adenosine Research Articles

Effects of sinefungin and 5′-deoxy-5′- S-isobutyl-adenosine on lipopolysaccharide-induced proliferation and protein N-methylation of arginyl residues in murine splenic lymphocytes

The effects of sinefungin (SF) and 5′-deoxy-5′- S-isobutyl-adenosine (SIBA) on lymphoproliferation and protein N-methylation of arginyl residues were investigated in splenic lymphocyte culture in vitro. Both SF and SIBA produced a dose-related inhibition of the lymphoproliferative response to lipopolysaccharide (LPS). The time-course of the inhibition indicated that SIBA had a more inhibitory effect than that of SF at short incubation periods, but SF showed more inhibition when the incubation was prolonged. The effects of SF and SIBA on the lymphoproliferative response corresponded with their effects on the protein N-methylation of arginyl residues by protein methylase I.

Relationship between methylation status and expression of an epstein-barr virus (EBV) capsid antigen gene

The methylation status of the 160 kD viral capsid antigen ( VCA ) gene promoter was determined by hybridization analysis. The semi-permissive marmoset cell line FF41-1 lacked cytosine methylation in approximately three quarters of the VCA promoter CpG dinucleotide residues. In the stringently infected HH514CL16 cell line the same CpG residues were methylated in three quarters of the genomes. 5′deoxy-5′-S-isobutyladenosine (SIBA), a DNA methylase inhibitor, was utilized to disrupt the EBV latent state. As determined by flow cytometry, SIBA treatment significantly increased expression of VCA. The VCA promoter was hypomethylated in VCA-positive FF41-1 cells sorted by flow cytometry. While hypomethylation alone was not sufficient for VCA transcriptional activity, the absence of methylation of VCA promoter CpG dinucleotide residues was associated with expression of VCA.

Effect of p-aminobenzoic acid N-xyloside sodium salt (K-247) on metabolism and functions of normal lymphocytes and leukemic cells.

An N-xyloside derivative of p-aminobenzoic acid, K-247, was investigated for the ability to induce changes of Phospholipid metabolism and membrane transport in murine splenic lymphocytes and leukemic cells. K-247 induced an increase of [3H] methyl group incorporation into phospholipid in both normal lymphocytes and leukemic cells (L-1210 and M1 cells). However, K-247 accelerated the turnover of phosphatidylinositol (PI) measured by [32P] incorporation into PI in L-1210 cells and Ml cells but not in normal lymphocytes. 45Ca2+ influx into normal lymphocytes and leukemic cells was also increased by K-247. A methyltransferase inhibitor, 5'-deoxy-5'-S-isobutyl adenosine (SIBA), suppressed both the increase of phospholipid methylation and that of Ca2+ influx. It seemed that Ca2+ transport might be regulated by membrane phospholipid methylation. On the other hand, K-247 was found to suppress [3H] aminoisobutylic acid (AIB) uptake into L-1210 cells and Ml cells. Protein synthesis in L-1210 cells and Ml cells slightly decreased but RNA and DNA syntheses in both normal and leukemic cells were not affected by K-247. These results suggest that K-247 mainly acts on cell membranes, which are more sensitive to K-247 in leukemic cells than in normal lymphocytes. K-247 also induced differentiation of Ml cells into macrophages and granulocytes with phagocytic activity and morphological characteristics. Moreover, K-247 elevated the Con A response of murine thymocytes, most of which were immature T cells and had low reactivity to Con A, and caused a decrease of Thy 1.2 antigen on thymocytes. It seemed that K-247 also affected maturation of thymocytes.

The effect of adenosine analogues on the in vitro growth of Trypanosoma cruzi

Trypanosoma cruzi (Brazil strain) was maintained in liver infusion tryptose medium supplemented with 5 or 10% foetal calf serum at 27 °C on a rotating shaker platform. 85 to 95% of the organisms under these conditions are epimastigotes and the medium supported logarithmic growth for up to 24 hours. The effect of S-isobutyl adenosine and Sinefungin R against cultured T. cruzi epimastigotes was studied: growth rate was slowed by both in a dose-dependent fashion; 500 μm Sinefungin caused complete inhibition which was irreversible after 24-hour exposure but the effect of S-isobutyl adenosine (1000 μm) was reversible. Motility and morphology appeared to be unaffected.

Effect of 5?-deoxy-5?-S-isobutyladenosine on hematopoietic stem cells

Unlike known cytostatics, 5'-deoxy-5'-S-isobutyladenosine (SIBA) does not inhibit proliferative activity of hemopoietic stem cells of intact bone marrow. On the contrary, it raises CFUs number of 15-28% in vitro and in vivo. SIBA inhibits by 40% the 3',5'-cAMP-induced increase in CFUs proliferation.

Mechanism of the concanavalin A-induced change of membrane fluidity of chicken erythrocytes.

When chicken erythrocytes labeled with a stearic acid derivative spin label was treated with concanavalin A (Con A), ESR spectra showed a change in the peaks due to the labels in membrane lipids, indicating an increase of membrane lipid fluidity. Addition of Con A increased the fluidity rapidly. This change was reversible only up to 30 min after adding Con A, and thereafter it gradually became irreversible. However, if the erythrocytes were treated with cytochalasin B and methyl alpha-D-mannoside, a complete return of fluidity to the normal level could be observed at any stage after the binding of Con A. The observation of freeze-fracture replicas of erythrocyte membranes by transmission electron microscopy also showed that the redistribution of intramembranous particles gradually became irreversible after exposure to Con A. These results suggest that the microfilament-like system, which modulates the distribution of cell surface receptors for Con A, participates in the modulation of membrane fluidity. Phospholipid methylation of chicken erythrocyte membrane was stimulated immediately after the binding of Con A. A methyltransferase inhibitor, 5'-deoxy-5'-S-isobutyl adenosine, abolished the increase of membrane fluidity within the first 10 min and also that occurring later than 60 min after adding Con A, but it was without effect on the elevated fluidity found between 20 and 60 min. Removal of extracellular Ca2+ had an inhibitory effect on the lasting increase of fluidity. These results suggest that the first increase of membrane fluidity by Con A may be caused by phospholipid methylation, while the second increase may depend on the rearrangement of Con A receptor glycoproteins through cross-linking wit Con A. The irreversible part of the membrane fluidity increase probably depends on Ca2+ influx, phospholipid methylation, and peripheral membrane proteins which constitute the microfilament-like system at the membrane inner surface.

The antifungal antibiotic sinefungin as a ver y active inhibitor of methyltransferases and of the transformation of chick embryo fibroblasts by rous sarcoma virus

The antifungal antibiotic Sinefungin is a structural analogue of S-adenosyl-methionine (SAM) and of S-adenosyl-homocysteine (SAH). It is as active as the synthetic SAH analogue S-isobutyl adenosine (SIBA) in inhibiting Rous Sarcoma Virus (RSV) induced transformation of chick embryo fibroblasts (CEF) in cell culture. Sinefungin, like SAH and SIBA is a competitive inhibitor in vitro of tRNA methylases and of protein methylases I and III of CEF. Its ki value for tRNA methylases of normal and transformed cells is respectively 3 to 10 times lower than the ki of SAH. It is thus in vitro the most active tRNA methylase inhibitor described until now. Protein methylase I and III are inhibited to about the same extent by the two molecules whereas SIBA has much higher ki values for the three enzymes in vitro. When methylation was measured in whole cells SAH, SIBA and Sinefungin inhibited (14C)-methyl incorporation to about the same degree in normal cells, but only SIBA and Sinefungin were active in transformed cells.Download : Download full-size image

Effect of 5′-deoxy-5′-S-isobutyl-adenosine (siba) on mouse mammary tumour cells and on the expression of mouse mammary tumour virus

5′-deoxy-5′-S-isobutyl-adenosine (SIBA), an analogue of S-adenosyl-homocysteine, inhibits the growth of mouse mammary cells transformed by mouse mammary tumour virus (MMTV) and the synthesis of MMTV particles in confluent cells. This compound modifies also the activity of reverse transcriptase (RNA dependent DNA polymerase) associated with MMTV particles. The stimulation of MMTV synthesis by dexamethasone is suppressed with low concentrations of SIBA.

Antimalarial activity of S-isobutyl adenosine against Plasmodium falciparum in culture

The continuous culture of the human malarial parasite Plasmodium falcipantm [l] provides a convenient new method for testing materials for antimalarial activity. Especially suitable for this purpose is the petri dish technique [2] . This method has now been used to demonstrate a new class of substances with antimalarial action, S-isobutyl adenosine (SIBA) and certain of its analogues. These analogues of S-adenosy1 homocysteine have been shown to inhibit several oncogenic viruses [3-S] and mitogen-stimulated blastogenesis of lymphocytes [6].

Inhibition oftRNA methylation in vitro and in whole cells by an oncostatic S-adenosyl-homocysteme (SAIl) analogue: 5′ deoxy 5′ -S-isobutyl adenosine (SIBA)

A high increase in the amount of methylated tRNA bases was found in vivo in Rous sarcoma virus infected and transformed chick embryo fibroblasts in comparison with normal cells, tRNA methylases extracted from transformed cells showed also higher activity in vitro with a heterologous substrate. 5'-deoxy-5'-S-isobutyl adenosine, (a structural analogue of S-adenosyl-L homocysteine), which inhibits virus-induced cell transformation, inhibits also the increase of incorporation of labelled methyl groups into tRNA in infected and transformed cells. When normal cells are grown in the presence of this inhibitor, undermethylated tRNAs are obtained. The effect of the drug is different in normal, infected and transformed cells. The methylation of the different bases is inhibited in vitro and in vivo to various extent. The effect of this substance on tRNA methylation may be the cause of its inhibitory effect on cell transformation.

Inhibition of viral RNA methylation in herpes simplex virus type 1-infected cells by 5' S-isobutyl-adenosine

5' S-isobutyl-adenosine (SIBA), a structural analogue of S-adenosylhomocysteine, reversibly blocks the multiplication of herpes simplex type 1 virus. In the presence of SIBA, viral protein synthesis is inhibited. After removing SIBA the synthesis of proteins starts rapidly again. The new polypeptides are mainly alpha proteins (Honess and Roizman, J. Virol. 14:8-19, 1974,), normally the first to be synthesized after infection. The rapid synthesis of proteins after release of inhibition seems to be directed by mRNA formed in the presence of SIBA as indicated by experiments using actinomycin D but which was undermethylated as shown by analysis of methyl groups on RNA. SIBA inhibits the methylation of mRNA and especially that of the 5' cap. Capping of mRNA thus seems to be essential for efficient translation. The analogue affected various methylations to different extents.

Inhibition of mitogen induced blastogenesis by 5′-deoxy-5′-S-iso-butyl adenosine

The mitogen induced blastogenesis of human and rabbit lymphocytes is strongly inhibited by 100 and 300 μM 5′-deoxy-5′-S-isobutyl-adenosine (SIBA) (I), a synthetic analogue of S-adenosyl-homocysteine (SAH) which had previously been shown to prevent oncogenic transformation of chicken fibroblasts by Rous Sarcoma virus (15). Addition of 300 μM SIBA even 1 to 2 days after stimulation by Con A or a Water soluble mitogen from Nocardia (NWSM), inhibited strongly the incorporation of [ 3H] thymidine. Lymphocytes recovered their ability to be stimulated by T or B mitogens after elimination of the inhibitor from the cultures.

Inhibition of virus-induced cell transformation by synthetic analogues of S-adenosyl homocysteine

Summary 1 mM 5′-deoxy-5′-S-isobutyl-adenosine (SIBA) (I), a structural analogue of S-adenosyl-homocysteine (SAH), inhibits the oncogenic transformation of chick embryo fibroblasts (CEF) infected with Rous sarcoma virus (RSV). When SIBA remains in contact with infected cells for 48 hours the inhibition of focus formation is irreversible, at least for 8 days. Virus replication is also strongly inhibited by SIBA. Normal CEF are only reversibly inhibited by this compound. SAH, the natural inhibitor of SAM dependent transmethylases has no effect on cell transformation.