2′-Deoxyadenosine selectively kills nonneuronal cells without affecting survival and growth of chick dorsal root ganglion neurons

Abstract

Recently, we have demonstrated that adenosine and 2′-deoxyadenosine are toxic to embryonic sympathetic neurons and proposed that purine and pyrimidine metabolism may play a critical role in the growth and development of sympathetic neurons. To extend this hypothesis further, we examined the effects of these nucleosides on two other neuronal populations in the chick embryo, sensory dorsal root ganglion neurons and parasympathetic ciliary ganglion neurons. Now, we show that 2′-deoxyadenosine and adenosine have no visible adverse effect on the viability of either sensory or parasympathetic neurons. Instead, 2′-deoxyadenosine proved to be highly toxic to the nonneuronal cells. The toxic effects of 2′-deoxyadenosine were markedly enhanced by inhibition of adenosine deaminase. In contrast, adenosine was much less toxic to nonneuronal cells than 2′-deoxyadenosine and its effect was not potentiated by inhibition of adenosine deaminase. Priming of pyrimidine pools by exogenous uridine and the specific inhibitor of the nucleoside transporter, nitrobenzylthioinosine, did not protect nonneuronal cells from 2′-deoxyadenosine toxicity. Since phosphorylation of internalized nucleosides was a key step in the initiation of toxicity in sympathetic neurons, adenosine kinase activity was compared in sensory and sympathetic neuronal cultures. The adenosine kinase activity in dorsal root ganglion cultures was only 20% of that in sympathetic ganglion cultures. Furthermore, inhibition of phosphorylation by blocking 2′-deoxyadenosine kinase with iodotubercidin and 5′-amino-5′-deoxyadenosine had no protective effect against 2′-deoxyadenosine toxicity. [ 3H]-thymidine incorporation was inhibited over 90% by 2′-deoxyadenosine as early as 6 h following its addition and for up to 4 days, suggesting inhibition of proliferation of nonneuronal cells by 2′-deoxyadenosine. The nucleoside was also able to wipe out already well established nonneuronal cells, leaving behind an enriched population of sensory neurons. The selective vulnerability of nonneuronal cells to 2′-deoxyadenosine offers a convenient and effective tool for removing nonneuronal cells from neuronal cultures as well as providing a new model for studying the mechanisms of nucleoside toxicity.