Increased cellular levels of spermidine or spermine are required for optimal DNA synthesis in lymphocytes activated by concanavalin A.

Abstract

There are large increases in cellular levels of the polyamines spermidine and spermine in lymphocytes induced to transform by concanavalin A. The anti-leukemic agent methylglyoxal bis(guanylhydrazone) (MGBG) that in the absence of increased cellular levels of polylmines, lymphocytes progress normally from Go through G1 and into S-phase. Furthermore, these experiments suggest that the increased levels of spermidine and spermine generally seen in rapidly proliferating eukaryotic systems are necessary for enhanced rates of DNA replication. Stimulation of the rate of biosynthesis of the aliphatic polyamines spermidine and spermine appears to be an invariable correlate of increased cell proliferation. Striking increases in the levels of the enzymes of polyamine biosynthesis and, to a lesser extent, enhanced cellular levels of these compounds have been observed in a variety of systems (1-5). Although the general phenomenon has been well described, and a variety of hypotheses have been advanced to explain the role of increased polyamine levels, few experiments have been designed to directly test the role of these compounds. Recently, with the discovery of specific inhibitors of polyamine synthesis, a new avenue of experimentation has become accessible. Williams-Ashman and Schenone demonstrated methylglyoxal bis(guanylhydrazone) (MGBG) to be a potent inhibitor of S-adenosylmethionine decarboxylase (6). More recently, Snyder and his coworkers have shown that a-hydrazinoornithine inhibits the conversion of ornithine to putrescine, the biosynthetic precursor of spermidine and spermine, both in vitro and in tnvo (7,8). If these inhibitors are specific for polyamine biosynthesis, and exhibit no other pharmacological actions, they will be powerful tools to examine the cellular function of the polyamines.We have used MGBG to study the role-of polyamines in lymphocytes which have been stimulated by concanavalin A (Con A) to grow and divide. MGBG rapidly brings about complete inhibition of the biosynthesis of spermidine and spermine when added to activated lymphocytes (9, 10). From the studies to date, it is clear that normal transcription and translation continue after polyamine accumulation is blocked with MGBG. We have therefore concluded that the increased cellular levels of polyamines seen in proliferating cells are not involved in protein synthesis or in the synthesis, processing, and accumulation of RNA (10). Hence, in defining a role for the enhanced polyamine levels, our attention has been directed to later events in the process of lymphocyte activation. Specifically, we have been examining the effects of MGBG on DNA replication and cell division (11). We demonstrate in this paper that blocking polyamine accumulation with MGBG leads to decreased rates both of [methyl-3H]thymidine incorporation into DNA and of cell division. Evidence is presented which strongly argues that these effects of MGBG are due directly to inhibition of spermidine and spermine accumulation and not to a pharmacological action of MGBG unr...

Reversible inhibition of rat liver regeneration by 1,3‐diamino‐2‐propanol, an inhibitor of ornithine decarboxylase

“…As shown in the present results, peroral diaminopropanol produced a virtually complete prevention of rat liver regeneration as judged by the ultimate variable of the regeneration process, namely liver weight gain. In aggreement with [7][8][9]27,28], the synthesis of DNA seemed to be affected mostly while the synthesis of RNA apparently proceeded as in the absence of the inhibitors or, according to the present results, even at an enhaflced rate.…”

“…The prevention of polyamine accumulation by competitive inhibitors of omithine decarboxylase [23][24][25] or inhibitors of adenosylmethionine decarboxylase [26][27][28][29] under a variety of experimental conditions involving accelerated growth appears to result in profound disturbances in cell proliferation, especially in DNA synthesis. Indirect amine inhibitors of omithine decarboxylase (such as 1,3-diaminopropane), which may act through an induction of protein inhibitors to the enzyme [30] or through more direct transcriptional or translational control mechanisms [31 ], have likewise been employed to abolish polyamine accumulation in regenerating rat liver [7][8][9], in rat liver during refeeding [32] and ovary cells grown in culture [33].…”

Inhibitors of polyamine biosynthesis affect the expression of genes encoding cytoskeletal proteins

“…Although the physiological functions of these compounds are still not well understood, several studies have shown that normal cellular growth and division require polyamines [2][3][4][5]. Direct support for this notion has been provided by experiments in which polyamine synthesis was prevented by the application of inhibitors [6][7][8]. Methylglyoxal-bis[quanylhydrazone] (MGBG), an inhibitor of S-adenosylmethionine decarboxylase, and difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, are most widely used drugs inhibiting key polyaminebiosynthesizing enzymes.…”

Polyamine-induced DNA Synthesis and Mitosis in Oat Leaf Protoplasts

“…Recently, substantial evidence has accumulated suggesting an important role of polyamines in regulating DNA synthesis (5,7) and an orderly progression through the animal cell cycle (9,13,24). For example, specific inhibitors of polyamine synthesis have been shown to prevent certain mammalian cells from entering mitosis (12,24), while addition of spermidine or spermine to such cells results in rapid resumption of cell division (7,21).…”