All along the watchtower: on the regulation of apoptosis regulators

Involvement of polyamines in apoptosis. Facts and controversies: effectors or protectors?

The natural polyamines (putrescine, spermidine and spermine) are ubiquitous low-molecular aliphatic amines that play multifunctional roles in cell growth and differentiation. Recently, evidence has merging that polyamines are actively involved in cell death. Changes in polyamine homeostasis have been reported during cell death of nerve cells, in programmed cell death of embryonic cells and in various in vitro models of apoptosis. Polyamines and many of their structural analogs exert cytotoxic effects in vitro as well in vivo. Furthermore, polyamine analogs and inhibitors of the polyamine anabolic/catabolic pathways modulate processes of cell death in a cell-type specific way. Much ambiguity exists in the working mechanisms by which polyamines mediate apoptosis since they have been shown to act as promoting, modulating or protective agents in apoptosis. Nevertheless, from the studies reviewed here it can be concluded that polyamines are critically involved in cellular survival which makes them suitable targets for therapeutic intervention that is specifically directed to cell death pathways.

Apoptosis in human disease: a new skin for the old ceremony?

Naturally occurring cell death or apoptosis is essential for the maintenance of tissue homeostasis and serves to remove extraneous or dangerous cells in a swift and unobtrusive manner. Recent studies have indicated a role for apoptosis in a plethora of human diseases. Hence, dysregulation of apoptosis has been implicated in autoimmune disease, acquired immune deficiency syndrome, and other viral (and bacterial) infections, as well as in neurodegenerative disorders and cancer. Furthermore, dysregulated apoptosis signaling may impinge on other age-related disorders such as osteoporosis and atherosclerosis and perhaps on the process of aging itself. The present review provides an overview of human diseases, which are associated with defective or inadvertent apoptosis, with examples of pathological conditions in which putative apoptosis defects have been elucidated at the molecular level. Novel apoptosis-modulating therapeutic strategies are also discussed.

Inhibition of cell death in human mammary epithelial cells by the cooked meat-derived carcinogen 2-amino-1-methyl-6-phenylimidazo[4, 5-b]pyridine

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mammary gland carcinogen present in the human diet in cooked meat. To examine if PhIP and its reactive metabolite N-hydroxy-PhIP inhibit apoptosis in human mammary epithelial MCF-10A cells, confluent cultures deprived of serum and growth factors were incubated for 24 h with either compound. The percentages of dead cells (mean +/- SEM, n = 3) as measured by trypan blue exclusion were 5.7 +/- 0.6, 3.4 +/- 0.3, 2.7 +/- 0.3, and 0.2 +/- 0.003%, in control, 1 microM N-hydroxy-PhIP-, 5 microM N-hydroxy-PhIP-, and 100 microM PhIP-treated dishes, respectively. The expression of Bcl-2 and Bcl-x(L) as quantitated by Western blotting was 1.2- to 1.9-fold higher in the treated groups. PhIP-DNA adducts induced by N-hydroxy-PhIP in MCF-10A cells measured by the (32)P-postlabeling assay were low (<1 x 10(7), relative adduct labeling). No adducts were detected after incubation with PhIP. Western blot analysis indicated that PhIP increased ERK2 phosphorylation concomitant with Bcl-2. The results suggest that the inhibition of cell death in mammary epithelial cells by PhIP occurs independently of PhIP-DNA adducts and may involve enhanced signaling through the MAP kinase pathways.