Mammalian cell polyamine homeostasis is altered by the radioprotector WR1065

Abstract

Mammalian cells become more susceptible to radiation-induced death and mutagenesis when restricted in their production of the natural polyamines putrescine, spermidine and spermine. The effects of polyamine deprivation are reversed by N-(2-mercaptoethyl)-1, 3-diaminopropane (WR1065), a simple aminothiol that has been extensively studied for its radioprotectant properties. Because this compound and its oxidized derivative WR33278 bear some resemblance to the polyamines, it was hypothesized that radioprotection by WR1065 or its metabolites is derived, at least in part, from their ability to supplement the natural polyamines. To evaluate the ability of these aminothiol compounds to emulate polyamine function in intact cells, rat liver hepatoma (HTC) cells were treated with radioprotective doses of WR1065; the ability of this compound to affect various aspects of normal polyamine metabolism was monitored. Although cellular WR1065 was maintained at levels exceeding those of the polyamines, this aminothiol did not have any polyamine-like effect on the initial polyamine biosynthetic enzyme, ornithine decarboxylase, or on polyamine degradative reactions. On the contrary, treatment with relatively low levels of WR1065 resulted in an unexpected increase in putrescine and spermidine synthesis. WR1065 treatment enhanced the stability, and consequently the activity, of ornithine decarboxylase. This stabilization seems to result from a WR1065-induced delay in the synthesis of antizyme, a critical regulatory protein required in the feedback modulation of polyamine synthesis and transport. The increase in cellular spermidine induced by WR1065 might explain its antimutagenic properties, but is probably not a factor in protection against cell killing by radiation. This is the first evidence that compounds can be designed to control polyamine levels by targeting the activity of the regulatory protein antizyme.

The cytoprotective aminothiol WR1065 activates p21waf-1 and down regulates cell cycle progression through a p53-dependent pathway

“…WR1065 and its oxidized dissul®te linked WR33278 show chemical structures similar to those of naturally occurring polyamines such as spermidine (Wyatt et al, 1989;Mitchell et al, 1998). To determine whether spermidine may also activate p53, we treated MCF-7 cells with increasing concentrations of either WR1065 or spermidine.…”

Structure–activity analysis of the potentiation by aminothiols of the chromosome‐damaging effect of bleomycin in G0 human lymphocytes

“…Aminothiols protect against ionizing radiation by scavenging hydroxyl radicals, transferring hydrogen to DNA radicals, and causing hypoxia near DNA [Purdie et al, 1983;Schwartz et al, 1988;Smoluk et al, 1988a;Hospers et al, 1999]. Other mechanisms that may contribute to radioprotection by WR-1065 are its causing increased synthesis of radioprotective polyamines [Mitchell et al, 1998], protecting sulfhydryl enzymes [Hospers et al, 1999], affecting enzymes of DNA synthesis [Grdina et al, 1994], and facilitating DNA repair [Grdina et al, 1999;Hospers et al, 1999]. Radioprotective effects of the polyamines spermine [Chiu and Oleinick, 1997] and spermidine [Newton et al, 1997] can be ascribed to scavenging of hydroxyl radicals and the compaction or stabilization of chromatin.…”

WR1065 mitigates AZT‐ddI‐induced mutagenesis and inhibits viral replication

“…Ames and Dubin [1960] reported that polyamines inhibited replication of T4 bacteriophage. Mitchell et al [1998] showed that WR1065 increased intracellular spermidine levels in cells exposed in vitro. Such a change has been suggested to have antimutagenic effects because of the DNA protective capacity of spermidine, and also could result in antiviral effects because of changes in intracellular polyamine levels [Bachrach and Rosenkovitch, 1972;Bachrach, 2007].…”