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  • Title: The bis(adenosin-N6-yl)alkanes, a family of potential dinucleoside-polyphosphate analogue precursors. Cytotoxicity, adenosine-receptor binding and metabolism.
    Author: Chen H, McLennan AG.
    Journal: Eur J Biochem; 1993 Jun 15; 214(3):935-44. PubMed ID: 8391440.
    Abstract:
    A series of bis(adenosin-N6-yl)alkanes, in which two adenosine residues are linked via their N6 positions by alkyl bridges comprising between 2 and 14 methylene units, were synthesized as potential precursors to dinucleoside-polyphosphate analogues. These compounds were moderately cytotoxic to mammalian cells, the toxicity increasing with the length of the alkyl chain. For example, the dose of bis(adenosin-N6-yl)dodecane, A[CH2]12A, leading to 50% inhibition of cell growth (ID50) for BHK fibroblasts, Walker 256 carcinoma cells and S-49 T-lymphoma cells were 90 +/- 8, 100 +/- 5 and 23 +/- 4 microM respectively. A significant amount of A[CH2]12A bound to serum albumin in the growth media; thus the ID50 for S-49 cells grown in serum-free medium was 9 +/- 2 microM. The corresponding bis-cytidine analogues were much less toxic; however the presence of a second adenosine moeity/molecule had little significant effect on cell growth when compared to N6-alkyladenosines. Toxicity to S-49 cells was unaffected by the nucleoside-transporter inhibitor nitrobenzylthioinosine and was even higher (ID50 = 5 +/- 0.5 microM) towards nucleoside-transport-deficient AE-1 cells, showing that the analogues could pass freely through the plasma membrane. Interaction with A1 adenosine receptors was shown by displacement of [3H]N6-R-phenylisopropyladenosine (Kd = 6 nM) from rat adipocyte membranes, with Ki values of 45, 65, 85 and 390 nM for the compounds containing 12, 8, 6 and 4 methylene units, respectively. Affinity for human platelet membrane A2 adenosine receptors was about 100-fold less, however the compounds were weak A2 agonists, producing up to a threefold increase in intracellular cyclic AMP in WI-38/VA-13 cells. Thus, these compounds behave, not surprisingly, as adenosine analogues. In addition, A[CH2]12A was metabolized in vitro and intracellularly by adenosine kinase (Ki = 70 nM) and adenylate kinase to yield a number of phosphorylated derivatives with the potential to act as diadenosine polyphosphate analogues. One of these, the bismonophosphate, was recognized by and inhibited adenylate kinase more effectively than adenosine(5')tetraphospho(5')adenosine (Ap4A, Ki = 3 microM).
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