Caspase activation in etoposide‐treated fibroblasts is correlated to ERK phosphorylation and both events are blocked by polyamine depletion

Abstract

Activation of the extracellular signal-regulated kinases (ERKs) 1 and 2 is correlated to cell survival, but in some cases ERKs can act in signal transduction pathways leading to apoptosis. Treatment of mouse ¢broblasts with 20 W WM etoposide elicited a sustained phosphorylation of ERK 1/2, that increased until 24 h from the treatment in parallel with caspase activity. The inhibitor of ERK activation PD98059 abolished caspase activation, but caspase inhibition did not reduce ERK 1/2 phosphorylation, suggesting that ERK activation is placed upstream of caspases. Both ERK and caspase activation were blocked in cells depleted of polyamines by the ornithine decarboxylase inhibitor K K-di£uoromethylornithine (DFMO). In etoposide-treated cells, DFMO also abolished phosphorylation of c-Jun NH 2 -terminal kinases triggered by the drug. Polyamine replenishment with exogenous putrescine restored the ability of the cells to undergo caspase activation and ERK 1/2 phosphorylation in response to etoposide. Ornithine decarboxylase activity decreased after etoposide, indicating that DFMO exerts its e¡ect by depleting cellular polyamines before induction of apoptosis. These results reveal a role for polyamines in the transduction of the death signal triggered by etoposide. ß

Lysophosphatidic acid prevents apoptosis of Caco-2 colon cancer cells via activation of mitogen-activated protein kinase and phosphorylation of Bad

“…Previous studies have shown that etoposide-induced apoptosis of fibroblasts and keratinocytes is associated with an increase in Erk phosphorylation [51,52]. In fibroblasts, etoposide induced caspase activity, which was completely abrogated by inhibition of Erk activity [51,52]. In keeping with these reports, apoptosis of hepatocytes by Clostridium difficile toxin is accompanied by acute stimulation of Erk [53].…”

“…On the other hand, etoposide alone resulted in acute phosphorylation of Erk at 30 min and occasionally weak and delayed Erk phosphorylation at 12-24 h ( Figure 7A). Previous studies have shown that etoposide-induced apoptosis of fibroblasts and keratinocytes is associated with an increase in Erk phosphorylation [51,52]. In fibroblasts, etoposide induced caspase activity, which was completely abrogated by inhibition of Erk activity [51,52].…”

Polyamine-mediated Apoptosis of Alveolar Macrophages during Pneumocystis Pneumonia

“…This apoptosis is also characterized by mitochondrial damage and activation of caspase-9 (31,66), similar to what is seen in alveolar macrophages during Pcp. Polyamines can stimulate apoptosis of cells directly (32,34,35) or through the generation of ROS (67,68). Data of the current study suggest that polyamines induce apoptosis of alveolar macrophages via ROS during Pcp (Table 6).…”

“…These factors upset the redox potential of the cytoplasm and cause mitochondrial membrane damage and leakage of pro-apoptotic factors. The primary polyamines putrescine, spermine, and spermidine are all implicated in initiation of apoptosis, but spermine and N 1 -acetylspermine are more often involved in the direct toxic effects of polyamines on the membrane potential of the mitochondria (32,34). Spermine can directly activate caspase-3 in macrophage-like cell lines (35).…”

Ornithine decarboxylase activity in tumor cell lines correlates with sensitivity to cell death induced by histone deacetylase inhibitors

“…Putrescine is normally produced by ODC, but when ODC is inhibited, addition of putrescine to the culture medium restores normal polyamine levels (31). HCT116 cells pretreated with both DFMO and putrescine were as sensitive as control cells to increasing amounts of TSA, whereas cells pretreated with DFMO alone were more resistant to TSAinduced cell death ( Fig.…”